UPDATED AGAIN! Do you think getting shot with lighter BBs from an an upgraded gun would hurt more, less, or the same?
 

(I wanted to make this a poll, but apparently I took too long to type because you only have a 5 minute window. :rolleyes: )

Simple question for half-assed science time!

Your gun shoots X fps. Assume X is consistent and high enough that you would maybe think twice about shooting someone at close quarters.

Do you think putting lighter ammo in your gun would hurt someone more, less, or the same? (In other words, would the lighter BB transfer more, less, or the same energy?) Why?


Bonus related topic:

Many people transition to sidearms when getting into close quarters, since most guns nowadays shoot pretty hot. Now, other people bring up the fact that doing it for safety's sake is a little weird since modern gas pistols actually shoot at least as hot as most electric rifles nowadays.

All other things being equal, do you think putting lighter weight ammo (like, .12s) into your gas pistol would help this?


Updated with test results! See this post.


Updated with a small duplicate test using floral arrangement foam, and a penetration test between .12 and .43. See this post.

Heavier BB = more kinetic energy. Same as a real bullet.

And not all guns are consistant with delivering the same energy to BBs of different weights.

Case in point, my old KSC USP Compact. It shot 300 fps whether I used .20g or .25g BBs.

it's been proven that Heavier BBs WILL retain more energy over time and distance compared to a lighter BB, which in return results in more pain.

This is also why reasonably heavier ammo(eg, 0.20g vs 0.25g. Not like 0.20g vs 0.43g) with the same gun has FARTHER maximum and effective range than a lighter ammo. They are also able to take more hop before spinning up into the air compared to a lighter BB.

As for the GBB issue, the thing with gas is that if the BBs heavier, it stays in the barrel a longer period of time than a lighter ammo would. This effect in return gives the gas more time to expand thus producing more velocity. That's why sometimes you would see a gun shooting 300FPS with 0.20g and still shoot 300FPS with 0.25g BBs, it's because the BB stays in the barrel slightly longer.

I'd think that lighter rounds would hurt less, or at least, do less damage. Even though the muzzle energy is approximately the same (heavier rounds appear to be slightly better as capturing energy during the internal ballistics phase), the weight of the round itself affects density and momentum.

In theory (my theory, anyways), all else being equal, a heavier (denser) round would hurt more because it would cause more damage. It would do so by both deforming less (less energy loss to elasticity) and penetrating deeper (better retention of its energy during the terminal ballistic phase).

Kinetic Energy = 1/2 x Mass x Velocity^2

Simplified Kinetic Energy is proportional to the Product of Mass and the Square of the Velocity. So if you have a faster firing gun, the reason it hurts more when you use the same ammo is because there is more kinetic energy, just like you said.

When you fire an airsoft gun, the energy stored when the spring is compressed, in converted into energy carried by the BB. The spring will always transfer the same amount of energy to a BB, so according to the equation above an increase of mass result in a reduction of velocity. Conversely a reduction of mass for an equal amount of energy will result in an increase in velocity. The overall energy of the BB is always the same.

There are two things that affect how much the BB will hurt. First is the amount of energy the BB carries, and the second is impulse. Impulse simply is the amount of force applied over time. A high impulse (lots of energy over less time) tends to "hurt" more, while a low impulse (less energy over lots of time) "hurts" less. To visualize this, immagine a rubber ball, and a steel ball, both the same mass. A rubber ball imparts a lower impulse (less force per unit time) and a steel ball imparts higher impulse (more force per unit time) which is why you'd rather be hit by a rubber ball then a steel ball.

The difference in impulse between different BB weights is negligible if not non-existant since they are made of the same material more or less. Hence the amount a BB will hurt is only based on how much energy the BB is carrying WHEN IT HITS YOU.

This is where BB weights matter. A heavier (or technically speaking a more massive) BB has greater inertia. A lighter projectile will have less intertia and the force of friction/wind will affect it much more. A heavier projetile will have more intertia, and will not be as affected.

Therefore at point blank, both a 0.2g and 0.3g BB should "hurt" just the same. However at a longer distance, a 0.3g BB will maintain its velocity, and hence will hurt more.

I hope this helps you understand why it would hurt more or less :).

EDIT: Also, the reason why lighter BBs may hurt less esp in CQB conditions is because they have less inertia. Hence they would be decelerated by clothing more then a heavier BB which would have more inertia. There are other factors (gas behavior under compression, pressure and force, etc etc etc...) but the ones I have mentioned should be the major ones.

Correct and incorrect. An AEG's FPS is directly related to BB weight. Gas guns are not affected as much and retain higher FPS when shooting with heavier weights.

Sorry, there is nothing incorrect in what I said.

Explain please why my M16A3 PTW will shoot 0.25g BB at 497 fps but will shoot a .20g at 530 fps? 20% decrease in BB mass but only a 6.6% increase in velocity? Don't worry, I already know the answer.

My old Marui G3 shot 265 with 0.25g and 295 with .20g. Same BBs (I haven't changed brands in years). Same 20% decrease in mass, but now an 11% increase in velocity.

Not all guns are consistant, and you can't say across the board that an X change in weight = a set velocity change.

Different barrel lengths and how your hopup contacts the BB also affect it. If you have a gun with the same barrel and same length and same/similar hopup you'll get most likely get very close to the same results. 30 FPS going from .20 to .25 seems right. That's what I got with my AUG with stock TM barrel. Notice both your guns changed by 30 FPS.

Also, BB mass % won't = velocity %.

And gas guns are a whole different deal too.

Load two different bbs and shoot yourself.

IMHO from experience a heavier bb will hurt more as in the end there is more weight in the object there for more force being distributed. Load a .20 and then a .28 and shoot yourself in each foot and see how the difference is.. I.E case in point when shooting through grass the .20's will fucking go everywhere as where the .28's bust right through and chop that shit up like a kick ass lawnmower..

http://img205.imageshack.us/img205/3...versionxq1.jpg

in reference to this quote - backing it up.

Everything here is total truth.

That's certainly true - for AEGs you have a set spring and a set volume, etc. It always pushes the same amount of air at the same pressure when it fires.

GBBs on the other hand have the gas port of the magazine open for as long as it takes for the BB to exit the barrel. (At which point the chamber pressure drops, the shuttle valve flips, and the gas is then 100% directed to slide blowback, at the end of which closes the gas valve.)

How this affects the BB, I haven't been able to test since I haven't had enough gas guns and a chrono together at the same time to do it. I'd love to compare with an NBB (which I think should "act" more like an AEG's spring/cylinder setup.)

Yes, I know. So why then do velocity changes drift so wildly for so many different guns? You answered the question already, and it boils down to my original point that not all guns are consistant. I was correct and you just reiterated that.

I go to my CQB PTW with the exact same cylinder, identical hop-up and the velocity increases about 8%.

So, unless you can build a formula that takes into account every length of barrel with every type of chamber with every type of hop-up rubber with every weight of BB, then my point still stands.

Well, not always. The piston head o-ring takes time to expand, and the lube in the cylinder will play a huge part in how fast this happens. This is not constant over time (as effective lubrication is reduced over time) and susceptable to temperature as well. The faster that o-ring expands, the more air volume is available behind the BB.

Ever notice how a poorly lubed cylinder can have huge deviations in velocity? I've seen 30-50 fps in lots of cases, or how re-lubing (and changing nothing else) will bring velocities up and keep them consistant. This was an easy issue to see in the PTW, as you used to need to perform periodic, specific cylinder maintenance which included a cylinder re-lube.

Thats really cool. Where do you find stuff like that?

that's a really dumb theory you have there, 20% decrease in mass doesn't mean 20% increase in velocity.

things don't work like that, it always have to follow a formula. We'll keep it simple, you can find the difference in velocity between 0.20g and 0.25g using 2 physics formulas

F= ma
vf(squared) = vi(squared) + 2ad

F = force applied
m = mass
a = acceleration
vf = Final velocity when leaving the barrel
vi = initial velocity before force being applied(so in this case, zero)
d = distance traveled between vi to vf

did some calculations and here are the results(In the calculation, I'm assuming that it fires 400FPS with 0.25g)
I also neglect any friction force between barrel and BB during barrel travel, and hop up effect.

http://img521.imageshack.us/img521/4600/lg1002xe4.png

From my chrono results(and yours too) shows that the difference in velocity between 0.20 and 0.25g IS roughly 40FPS give or take a few FPS (because of hop up/friction).

so no, 20% mass decrease in mass does NOT equal 20% increase in velocity.

Keep in mind too if you took your gun with a mag with 0.20s, and then another with 0.25s, chances are the 0.20g bbs will be less affected by the hopup too. The 0.25s will push for longer, and push harder, upon the hopup then the 0.20s. I think so anyways.. lol.


EDIT: My point is that there are a lot of different things that come into play as to how much the speed will change when you change the BB weight.

I know this. I was using the % as a measure of change, not an actual "to be expected" result. Re-read my post again.

then why did you even say such a thing.... it proved like.... nothing.

But it did. If you read it, you'd see that the change should be uniform, if theory actually translates to practice. Clearly it doesn't, as there are variables that are not factored in to a simple mass/energy/velocity equation.

Guns are too inconsistant to apply a simple formula and expect to get the right answer all the time. Sometimes it works, but that's luck.

Neat FYI: http://www.airsoftcanada.com/showthread.php?t=51752

I took every chrono reading in that thread, threw them into Excel and worked out the energy for each, then averaged them for each BB weight and data set. I posted my conlusion somewhere here but the jist of it was that as you increase your BB weight, the total kinetic energy (minus rotational) increased by around 5% for the same gun - EXCEPT the .28's always wanted to decrease slightly for some reason.

The pain vs weight question is also something that has boggled my mind. With a quick test we were doing one day we took a 400fps gun and a 370fps gun and tested them at around an average to long typical airsoft engagement distance (probably around 100+' but I'm terrible with distances). The .25's on the 400fps gun hit noticeably harder and the .23's on the 370fps gun hit noticeably harder. Probably around a dozen shots or so with each weight at each fps and on the legs

Ever since I did that test, I've been skeptical and want to do some more maybe this winter or next season (note, test was also confirmed by a buddy as we took turns shooting each other).

I'd like to hear someone who knows what they're talking about talk about pain and what factors are involved. I don't think simply saying KE without any proof or reason is good enough; the body is a pretty complex system.

There's also this to look over: http://cybersloth.org/airsoft/trajectory/index.htm

I looked over his theory and it seemed pretty sound (I had a few qualms) however his lack of empirical evidence (which he claims he has) to back up his neat little theory was sketchy. Seemed to me like a typical engineer...if it doesn't fit your theory, you fudge things to make it look like you know what you're talking about so you don't appear to be wrong.

Fixed for you.

Not hard. Just enter the kinetic energy formula into excel spreadsheet.

What would be more impressive if you take into account air resistance at different temperatures.:p

I'd say heavier BBs inflict more pain.

Reason being that heavier BB tend to be more dense than lighter BBs assuming both BB are composed of the same material, the latter being less packed, microscopic pockets of air should absorb more energy than a heavier BB with a higher density. Less pockets of air will give you a better transfer of energy without energy being absorbed by the material itself.


Movies would be so much more interesting if we didn't take physics.

I think your graph is incorrect.

450fps with .20g should give 1.88j at the musle. So I guess other stats are also wrong.

I have good graphes somewhere that show everything you need to know about BBs ballistic, but it's not hosted on my server.

Edit: After closer inspection, the graph look fine. It's not very acurate, but it look fine. I retract my statements. But 450fps with .20g is still 1.88j.

That being said. Higher velocities with heavyer BBs require longer minimal engagement distances.
A 350fps (chronied with .2g) AEG require a minimal engament distance of 10fts using .25g in order to have 1j at impact.
Compared to a stock gun, 280fps with .2g require no MED since there is only about 0.7j at the musle.
Compared to these velocities.
400fps with .2g require a MED of 20fts using .25g BBs
450fps with .2g require a MED of 40fps using .30g BBs

So yeah, heavyer BBs punch harder and require longer MED.

I think you're reading it wrong. It says 450fps is almost exactly 1.88J with .20's

That's how I see it too, 450fps with .20s is approx. 1.88J give or take .01J

I would think that at close ranges pellet mass would not affect the damage/pain potential of an AEG. AEGs have shown themselves to be constant energy devices endowing a pellet with a consistent amount of kinetic energy despite varying pellet mass.

However I've found that the first 20' of flight can incur a significant velocity loss, especially with lighter pellets (shooting at a chrony at range).

I suspect that this is due to two causes:

-air resistance roughly varies with the square of velocity
-lighter pellets have lower energy density in terms of Joules/(fps)

A lighter faster pellet will experience significantly higher air resistance to a slower heavier (equivalent energy) pellet. That increased energy loss due to higher squared velocity will be compounded by the greater fps reduction when the pellet sheds kinetic energy from it's lighter body.


I have found GBBs and NBBs of many types to be significantly non constant energy devices, especially if they are propelled by a 2 phase compressed liquid-gas method (propane or HFC134a). I suspect that this is due to several factors:

-Higher initial pressures
-Higher gas density (propane (1.5x higher) and especially HFC134a (3.5x) have higher density than air)
-More complex pneumatic arrangement

Room temperature saturated propane exerts around 115psi. Conversely an AEG springs peak force results in a pressure of only 20psi (guesstimate based on the spring exerting 15lbf at full draw). The considerably higher pressure will experience a much higher initial flow rate which will incur much higher pressure losses over the convoluted pneumatic arrangement typical to most gas powered guns. I surmise that flow rate dependent pressure drops over the various valves and openings cause a considerable loss of pressure applied to the pellet.

For awhile I bashed my head against the question why such a high pressure didn't result in deadly velocities. If an AEG spring exerted such a small pressure in comparison to the saturated gas pressure of propane, why weren't propane guns dangerous?

First off, long barreled propane propelled rifles can exert very high velocities (500+ fps easily). Secondly, a magazine contained a relatively limited volume of pre expanded gas. Propane requires significant energy to boil off and maintain mag pressure so I suspect that the phase of pellet propulsion relies almost completely on the expanded gas.

This fixes the supply of gas phase propellant so you don't get a tremendously fast BB because the pressure starts to rapidly drop as gas expands through the gun and experiences pressure drops over all the various valves and orifices.

Propane and HFC134a have significantly higher density than air. Heavier gases experience higher pressure drops over flow resistances which will reduce the final pressure applied to a pellet. These pressure drops over flow resistances (valves and ports) will be dependent on the flow rate of the gas and apparent backpressure provided by the pellet. This means that the gas flow rate out of a gun is significantly dependent on the resistance to gas flow that a pellet presents. Therefore the pressure drops over various flow resistances will be ultimately pellet dependent.

I surmise that a funny issue of series resistance to gas flow situation arises in a gas airsoft gun. You start with a high initial pressure in the mag until the mag fire valve opens. Gas flows through the fire valve and mag rubber and nozzle body until it impinges on the back of the bb and starts it moving. Pressure builds up behind the pellet and gets it moving.

Even if the gas is dense compared to air, it's definitely not dense compared to the pellet so the gas flow starts to become dependent on how fast the pellet presently moves in the barrel.

I suspect that the pellet represents a resistance to gas flow which is in series with all of the other orifice resistances. Heavier pellets represent higher resistances to flow while lighter (faster accelerating pellets) represent a lower resistance.

This is the bit for DonP: This presents a funny series resistance situation analogous to an electrical series resistance where a fraction of power is dissipated over all of the series resistances. For the most efficient power delivery to the intended load (the pellet, or analogous motor in your circuit) you should maximize the resistance of the intended load to put most of the pressure (or analogous voltage) drop at your intended load.

In the case of lighter pellets, the pellet moves fast enough that it allows a higher flow which incurs higher pressure drops over the orifices and valves resulting in lower pressure applied to the pellet. Less pressure means less force for given distance which means less muzzle energy. Heavier pellets slug down the flow rate and put more of the pressure drop at the pellet which means higher muzzle energy.

So the heavier BB gets a bigger kick in the pants, because it allows the pressure that's built up behind it to be usable, and maximize efficiency. Where the lighter BB doesn't use the pressure build up behind it efficiently, and there is pressure loss through leaks in the mechanism before it can be used by the projectile. That all makes sense to me.
I am visualizing a water hose with water flowing out. You put your thumb over the end for just a second, and then release it and there is an increase in the flow from built up pressure. If you hold your thumb there again,but for longer this time, the pressure build up is greater, so when you release the flow again, the water will travel farther and faster.

In a nutshell that's kind of correct. However I don't think the pressure really build up so much as reach an equilibrium when the pellet gets moving. Initially almost all of the pressure drop is at the valves and orifices because the pressure on the other side of the mag valve is atmospheric pressure so the initial flow rate has almost all of the pressure drop right at the mag valve.

At some point pressure builds up and gets the pellet to pop past the hopup and start down the barrel.

The pressure drops I'm describing are not due to leaks so much as actual flow resistance. For instance if you crack open a valve on your BBQ tank a 115psi pressure drop occurs across the valve itself between the inside of the tank and the environment. Flow through the valve accelerates until all of the pressure drop occurs over the valve and you have a flow rate which drives a 115psi pressure drop over the valve resistance.

Imagine applying 30psi to one of a water hose to drive the water. At one end you've got 30psi. At the open end you've got 0psi (atmospheric) so you end up driving water as fast as 30psi can deliver over the entire flow resistance of the hose. No side leaks, just the flow resistance of the hose which delivers a certain flow rate of fluid for a given pressure drop.

Hahaha great minds think alike, I just edited with the water hose visual too. LOL

There's an easy way to settle this. Start a bizarre internet myth so the Mythbusters test it.

Call it the Savage Cheek (pick wehever one) Test for APP (airsoft projectile pain) factor.

^ truth

Actually, there are a number of correct things posted in this thread...and a little misinterpretation by some of what others are trying to put forward.

I ran a bunch of velocity tests when setting up a buddy's rifle for both CQB and outdoors with a single mechbox (I found playing with the barrel length far more interesting than fiddling with other variables).

It was boring and I'm not convinced of the results. Despite efforts to keep the tests practical and consistent...there are a lot of variables that come into play. I might repeat the tests again this winter if I get really bored...but I'd have to be really, really bored and it's basically a waste of money and time.

It sounds great and simple to say..."When you switch between 0.20g and 0.25g bbs, you'll drop 30fps"...but there's such a variance that even 10fps on a 400fps rifle is just 2.5% of the overall velocity and so pretty inconsequential given the system...and anyone who has tried to do these types of tests knows how easy a 10fps spread pops up. With a lot of data you can start to see trends...but what to do with the spread/%error? The comment becomes..."when you switch from 0.20g to 0.25g bbs, you'll get a 20-40fps drop" and starts to become useless as a guide line.

Extend this to encompass the fact that one airsoft gun's compression and setup can vary wildly when compared to another...and it's a very rough guideline at best. (I.e. take Stalker's uber +/- 1fps target grade bolt action and extend the results to a Kraken)

What is valid...is for each person to try out different BB weights and then to say..."In MY setup, going from 0.XXg to 0.YYg resulted in drop/increase from ABCfps to XYZfps". Unfortunately those results are limited to your rifle...and lose validity for another.

So far as GBB's...heavier bbs work better. With all the "target"/IPSC/CAPS shooting lately...it's painfully evident that when you want to shoot better than MOB (Minute of Body), and you want to shoot a consistent sub-palm size cluster...you shoot heavier BBs. Zero controlled tests to back this up...just practical observations. So far as what weight hits harder...that's easy to see after a night at the range...heavier BBs punch though the patched up metric targets better than the 0.20g lightweights that are often stopped/stuck in the target cardboard. ***edit*** but obviously simply switching to heavier BBs won't make an inaccurate GBB shoot like a tack driver***

To address the original question...heavier bbs hit harder than lighter BB in normal field/engagement ranges. I know this because I've been shot a lot. I also know that you should load 40mm grenades with lighter BBs...because they sting like a MoFo when you get blasted up close.

ahah yes recently I was testing with a shit chrony and at one point I got 700 fps.
That has to be an error ;)

in joules

0.2g@350=1138
0.2g@380=1340
0.2g@410=1561

0.3g@350=1707
0.3g@380=2011
0.3g@410=2342

So (unless my calculations are crappy crapola) if switching to 0.3 makes you lose roughly 30 fps, you will still gain from 300 to 500 joules at these speeds (including speed decrease), while a 30 fps increase at constant weight will only add 200 joules at 0.2g and 300 joules at 0.3g.

Uh Jimski, I hope airsoft pellets don't carry that kind of energy. Try going down about 3 powers of 10.

Check your units. You're off by a factor of 1000 (convert grams to kg???)

MadMax,

Have you seen this before: http://cybersloth.org/airsoft/trajectory/index.htm

I'm curious to get your take on it coming from another engineer.

That's one of the source we used to build our sniper ballistic charts and set our standards. I'v studied the whole thing and it's very good IMO.

Fox, I'm not trying to be condesending but were you able to understand and validate all of his theory? (because that's all I saw was theory and no empirical evidence he claims he has to support his theory). With the theory he covers you more than likely need an engineering degree to understand it; highschool physics won't suffice!

EDIT:

It's been a bit since I browsed through it but a few things I thought were off were:

- His coef of drag on a sphere: I think his theory was wrong IIRC
- IIRC he claims that the BB's will all hit their target in the same time amount reguardless of weight; seems counter intuitive to me.
- As I mentioned, the lack of imperical evidence to backup his theory which he claims he has and are damn near spot on.

ah yes I used grams
weird I thought the equation used m.s-1 and grams
crap wiki says it's kg
:) huhu

.28's hurt like a son of a bitch compared to .20's.

Based on my experience, what he demonstrated by his theory and backed by his testing In real life, is a good base to start from.

You want emperical study, go ahead, make your own study. But as far as I know, his study is the only one in existance that is complete and to the point. It may be an unproven theory, but that does not make it a bad one.

If you took the time, like me, to read ALL that stuff and pull out the valued and make your own calculations, you will know that this stuff is usefull to us and it can be applyed to the game.

Since the BBs and gun are inconcistant, thoses values are ment to be used as a base line.

ex: I made range card to be used with X weight of BBs at X fps. It also has mildots indications. I know for a fact that the mildots indication on my range cards won't result in a one shot one hit, but I know that it's a good estimation on where to start to acheive a one shot, closer to one hit than a blind shot... See what I mean?

As for the joules indications, it's the first time I see charts that take into account BB terminal velocities, air dencity, energy, range.... So for setting MED (Minimum engagement Distances), I think it's the best thing we have to work with.

I don't need a physic Ph.D to use these thing. I might not be able to fully understand his calculations and do my own to validate, but I know how to interprete the values and apply the theory on my experience.

Why not just get a chrony that can rate joules... and fire through it with the same gun at different distances with .2 and .3?

see which one retains more energy

Because it probably would not be an accurate test. It would shed some light on the relationship between exit velocities and BB weight, but the question here I understand is measuring impact energy. Some kind of test using a kind of ballistics gel with ranged tests would probably be more a long the lines of getting the answer people want. A .20gr bb will have retain more of its energy for a far greater time than say a .42gr, weight and back spin can compensate for cross-wind interference but ultimately the added weight slows down the BB dramatically when using the same power to launch the .20gr BB.

The problem I saw with Jimski's numbers before the answers, was that he guaged a .20gr compared to a .30gr with both having the same FPS. Now for what we are looking for, that is completely off the mark on the numbers. My bolt actions for instance would launch a .20 gr BB at 450fps while the .30gr would get aprox 350 out of the same energy. So the question starts to become is the reduction in speed countered by the increase of BB weight affect the outcome of overall impact strength. But I do not believe this stops simply at the exit velocity, because as I said, the heavier round will loose its speed faster than the lighter. This is why I'd think some sort of range test with a meter that can detect and measure the impact force; done at ranges of 20ft 40ft 80ft 100ft 150ft or along those lines would be more accurate to determine which is going to be "felt more".

The reason I really don't think that exit velocity is the real way to determine this is after some years I've noticed and have been talking to another local about the "Matrix effect." This is where after time you start to notice that you start tracking and instinctively start to "avoid" BB rounds as you see them coming at you. Now I'm not talking Super Neo on the rooftop here where you're over backwards cartwheeling your arms and so on. But you are able to start tracking the heavier rounds and as such it gives you a chance to avoid the round. Lighter rounds traveling faster become harder to see and as well harder to react in time at closer distances.

Lol fuck it! I'll just shoot people with whatever weight BB's I have handy!!

if you're pissed off bbs hurt more that's why I insult the enemy first usually

actually theres a slight calculation error in ur formula.
E=.5*m*s^2, where E is in joules, M is in KG, S is m/s
so a .2gram bb is .0002KGs, and at 100m/s = 330fps
E=.5* .0002 * 100*100
E=1 Joule

yes I took g instead of kg, silly me, 2000 J BBs :)

but what it says makes sense nevertheless, going heavier will hurt/penetrate more than going faster.

personnaly I choose faster BBs for CQB and heavier BBs for long range.

Best way to visuallise it.

Try hitting someone with a 45lbs weight in your hand. Slow, but devastating.
Now, hit the poor bastard with a 2lbs leather wip. Fast and paintfull.

So what?

The eavyer you hit, the more energy is transfered and the more damage is done. The lighter the hit, less damage.

We feel pain differently though. Both BBs will be painfull, but heavyer BBs are more prone to leave a mark on bare skin at equal velocities.

All that mess would be solved if we forget about fps and think only about joules.

OK, a quick recap. The question I posed myself (and you fellows) was "All other things being equal, would loading lighter ammo into the same gun cause less of an ouch?"

A practical application of this would be loading a gun (like a sidearm) with .12g BBs in order to make it more CQB-friendly. Could this be reasonably expected to help?

It seems some people think yes (heavier ammo = more energy = more ouch), some people think no (lighter ammo = higher FPS = same energy), and some people like to argue. :D

Well, nothing gets the brain working like a good experiment.

Disclaimer: I did specifically lay out that this was half-assed science time.

My hypothesis: Lighter ammo will overall transfer less energy, compared to heavier ammo from the same gun.

The test setup: Putty is used as a way to capture and visualize BB energy transferred. Shoot the putty from point-blank ranges with a variety of BB weights (.12g, .20g, .28g, .30g) from a variety of guns. Measure the results with a depth gauge, and eyeball the hole.

Why do it this way:
Three main reasons:

• The putty deforms when hit, and "freezes" when no more energy is spent deforming it. This is easy to measure and seems to be a consistent measure of energy transferred. As a side note, energy transfer should be optimal since the BB stays in full contact with the putty until it is no longer penetrating (energy transfer being a function of how long something can stay in contact over how much area, and all that. No glancing shots, etc.)
• It therefore doesn't matter that putty doesn't act like skin, or that skin in different spots feels pain differently. We're interested only in relative energy between different weight BBs from the same gun. As long as it's consistently measured, we're good.
• Shooting things that do something when you shoot them is fun.

Assumptions, Out Of Scope, etc:

• In all individual tests: Same gun, same propellant, same putty, same range.
• We are not measuring quantative energy, just relative energy between different weight BBs from the same gun. So converting "size of dent" into "joules" or whatever isn't in scope.
• The bigger/deeper the hole in putty, the harder the hit.
• The harder the hit, the bigger the OUCH potential.
• Only point-blank ranges are tested. Results valid at point-blank will be valid at longer ranges since it's impossible for a BB to go faster the further it goes.
• In other words, if a .12g BB doesn't hit as hard as .20g at point-blank, it never will no matter what range you go out to.
• How well energy is retained at longer ranges for different weights is out of scope. (Meaning whether .20g retains energy better at longer ranges than .12g is out of scope.)

TEST RESULTS

This is a typical target:
http://unconventional-airsoft.com/gf...cal-target.jpg

First up is a KJW 1911 Gas Blowback on duster at point-blank range (2m). NOTE THAT THE WHITE SPOTS INSIDE THE HOLES ARE PAPER FRAGMENTS. BBs DID NOT PENETRATE.
http://unconventional-airsoft.com/gf...911-Duster.jpg
Observations: There is a clear progression in penetration depth related to BB weight.

Next is the same KJW 1911 Gas Blowback, but this time with a CO2 magazine.
http://unconventional-airsoft.com/gf...2-1911-CO2.jpg
Observations: The relation of penetration to BB weight is still clear. Overall all BBs penetrated further. The CO2 mag was observed to shoot noticeably harder.

Next up is a KJW MK1 Non-blowback on duster.
The non-blowback should fire the BB with a fixed "gas charge" unlike a GBB which keeps the gas on as long as the BB is in the barrel. This surely has some kind of effect on BB fps, but that's not specifically of interest here -- does a NBB versus a GBB change the trend we're observing?
http://unconventional-airsoft.com/gf...MK1-Duster.jpg
Observations: Same progression observed -- more BB mass means more observed putty penetration.

Finally we have an APS2 bolt-action spring rifle.
http://unconventional-airsoft.com/gf...APS2-front.jpg
http://unconventional-airsoft.com/gf...-APS2-rear.jpg
Test 1 Observations: All BBs except for .12g penetrated into the backstop. Clearly .12g had less energy, but what about the rest?

Another test was done, this time with BDU material in front of the putty instead of a paper target.
http://unconventional-airsoft.com/gf...BDU-fabric.jpg
http://unconventional-airsoft.com/gf...ic-results.jpg
Observations: Same trend observed as all previous tests. Heavier weight from same gun = more penetration.

A NOTE ABOUT MEASUREMENTS
Two decimal places of measurement for a depth gauge into putty smacks of "measure with micrometer, mark with chalk, cut with axe." :) This is not lost on me. So I did a quick test where I shot the putty with 4 rounds of .20g and measured each. The measurements were remarkably consistent; biggest deviation was .12mm. Admittedly it's a small sample size (just like the rest of this experiment) but it looks like putty is not only consistent but the depth gauge is as well. At least, enough to see what I'm trying to see.


CONCLUSIONS

• Heavier BBs (i.e. more mass) fired from the same gun equals more energy transfer on impact. (Compared to lighter ammo)
• Lighter BBs (i.e. less mass) fired from the same gun equals less energy transfer on impact. (Compared to heavier ammo)
• The different mechanics of operation between a NBB versus a GBB versus a spring piston doesn't change this.
• Shooting stuff is pretty fun.

Therefore, while pain is subjective and depends on where and how one is shot, I think it would be reasonable to explore loading .12g BBs into a gun for the purposes of making it more appropriate for CQB - for example into a gas gun sidearm which otherwise might shoot pretty hot. (And CQB is an environment where the poor accuracy of .12g at range won't be much of an issue.)

Whether it actually makes enough of a practical difference to make a hot gun safer? Maybe!

^^ nice post lots of good info . this should be sticky

Nice work DonP!

I do have some concerns with your use of putty as a target media though:

-varying thickness in putty target
-many putties are non Newtonian

It seems that your putty pad isn't very thick. Thin pads bring the backstop into play when the putty deforms and backs into the rigid backstop. I would think that a very thick pad of putty (say 2") would reduce the effect of varying thickness to the backstop by taking the backstop out of the deformation behavior altogether.

Most putties tend to be non Newtonian. Their apparent stiffness is highly deformation rate dependent. Faster deformations may absorb more energy than slower ones which directly affects the damage potential we wish to observe.

I think it is also important to also measure the muzzle velocity just before the pellet impact. Making an assumption of constant energy may be a mistake when you're trying to correlate performance with damage potential.

2m is not exactly point blank in airsoft terms. IRC my shots at my Prochrono indicated up to 20fps velocity loss with high energy rifles shooting 0.2g pellets at 10'. Heavier pellets exhibited lower velocity loss. I think you need to blast your targets at 6" instead of 2m (~7')

Hmm, that's true. While my putty thickness was pretty even (used a roller and measured the first few, I didn't measure each and every one.

It's possible --- unlikely I think (but of course I would think that since it would go against my hypothesis) but possible that some of the BB impact areas were markedly thicker than others. But so much that it would throw off the observed trend? Maybe.

I did notice some BBs hits deforming the back of the putty pad (see the APS2 result for the .12g - it deformed the back even though it actually didn't penetrate that far.) This does affect the "toughness" of the putty, but I figured that the effect should be consistent across all the BB hits, and should all cancel out, no? Again, I'm probably just happily declaring immaterial something that would otherwise require me to set the test back up and challenge my assumptions. Screw that.

Hmm, this is a really good point I hadn't considered. Maybe ballistic gelatin would be better. But much messier and harder to set up, so therefore surely it wouldn't be worth trying!

Do you mean measure the muzzle velocity between different shots of the same BB weight to make sure I'm not getting the odd "hot shot" or something?

I don't see velocity being relevant otherwise, unless I'm missing your meaning.

EDIT: Oh, I think I get it. Repeating the tests at 6" might be interesting just to see if (and how much) .12g penetrates more at 6" as opposed to 2m. If there is a condition where lighter ammo possibly gets MORE penetration, I guess it would be right at the muzzle or never.

I'm guessing that the putty behaves incompressibly when it deforms so some sort of flow has to occur to create a bb crater. Given the flow-velocity issues I would think that it would be best to take the backstop out of the behavior and have the putty flow uninfluenced by a rigid backstop which imposes some funny shear behavior right at it's face. I would think that this factor would exacerbate the non Newtonian behavior of the putty.

I've been guessing that equivalent energy for different weight pellets would have the same potential for doing work when they smash into things. I suppose the only other absorption for energy (other than deformation) could be heat which could be significant for viscous media like putty which does transform a fair bit of work into heat when you knead it. I don't know how the heat issue translates into pain factor, but it's hard to measure the temperature rise in the immediate impact area and this would be unaccounted energy.

I've found AEGs to be largely constant energy devices, but when shooting very low weight pellets this behavior starts to break a bit (IRC it's been a really really long time since I did this battery of tests). I suspect that very light pellets offer such a low resistance to flow that other restrictions and the piston mass start to eat up more energy. This is why I suggest measuring impact fps. Also it does help to throw out the odd hot shot.

Now that I think of it, quantifying damage potential is a very difficult problem. The influence of speed and penetration are pretty well documented. At some point very very fast projectiles cause cavitation and end up destroying themselves in most ballistic media while slower heavier masses can achieve much deeper penetration. Our dinky balls operate in a completely different velocity regime, but I think it's hard to determine an accurate correlation between penetration and pain without using a media which actually simulates human flesh. I'm starting to come to a better appreciation of why the FBI chose ballistic gelatin because it offers a good analogue to tissue to assess penetrating damage.

In our very low energy situation with light projectiles, I think we need to choose a medium which is significantly less dense than our projectiles. It's obvious that dense media will significantly slow faster less dense projectiles with flow resistance, but I argue that this is not a good indication for low pain since our projectiles usually don't enter into the body and experience surface flow resistance.

I'm thinking we need a hybrid target that behaves in a Newtonian manner with an unpenetrated skin (like your cloth outer). Maybe a foam target that isn't resiliant with a cloth outer might be a good target. It would exhibit low rate dependent behavior and still provide a permanent deformation to assess. Maybe put a canvas cloth on that green sponge that flowers get stuck into.

Sorry, read that and just brought back memories of chronies with shattered LCD screens, made me laugh.

One guy I know says .28's can be easily dodged and .25's can't because of the fps difference, so to test it I got him to try to dodge .28's out of my M14 and .25's out of an M4. He started babbling some equations and physics at me (hes an engineer) and then I broke it to him that the M14 is shooting .28's faster than the M4 is shooting .25's (the M14 is semi only.)

All I know is with .28's you can't use foliage as hard cover very reliably but with .25's out of the same gun the leaves and branches stop the BB's in their tracks. Heavier BB's are also more accurate, and only wimps complain about weight differences causing extra hurt.

Very nice analysis. There's only one problem with it. You're using gas guns in which the FPS is affected less than an AEG. ex) Using heavier BB's does not translate to the same drop in fps as AEG's.

Barrel length factors in for AEGs. A short barrel AEG will behave that way, too.

Also, Don's original reason for posing the question was with respect to using GBBs in CQB/close range, and the safety claims that go along with that (and if using lighter ammo would be safer).

And there was an APS in there.

@Don: you could make some airsoft-caliber ballistics gel with some kitchen grade gelatin :)

We used to use plumbers putty as a back stop for pellet shooting. When we once did "testing" (really just goofing around), we used two sticks of equal thickness and a rolling pin to achieve a consistent thickness for the test medium. Same way that you grade gravel for interlocking brick.

We did find that you needed "extra" medium so that there would be enough give in the medium, otherwise an adjacent shot would tend to deform things too much. Maybe not a problem with yours as essentially a backer was used. (we used 2" thick free standing chunks)

It would be most interesting to repeat these test at a further distance to demonstrate the momentum effect of heavier bbs. 2m vs. length of basement.

Nice stuff!

Tys

It's simple, heavy BBs concerve their energy longer. They need longer MED to be safe at hight fps, like for snipers.

I like your putty test DonP. Even if it's not scientific, it's still a good example of what happend.

Now trie this. With the same gun, fire a .25g BB at 350fps at 10fts of your target.

From the same gun, load .20g but get closer.

See at what distance, the .20g BB will have the same impact penetration as the .25g BB.

At 350fps, a .25g BB will have about a 1j impact at 10 fts. That would be the MED for this velocity and weight.

To validate the MED thing, if you can try a 450fps rifle, shooting .30g at 40fts of the target, you should also see similar penetration as the .25g, since it take 40fts for a .30g at 1.88j (450fps) to attain 1j of energy. That's it's MED.

All fps values are mesured with .20g.

This may prove usefull.


http://ninjase.viscidity.com/trypsin/airsoftcalc/

This tells me that a .12g BB @ Around 580FPS has around the same energy as a .43g BB @ Around 306FPS

so less weight @ same speed = less energy

but in all fairness with are field limits do these really hurt all that bad (spare getting one on bare skin or a tooth at close range)

That's not a bad idea, I might try picking some up next time I'm at the 1$ store.

My favorite idea for a follow-up is human trials, though. Get shot with a .25 and a .12 from the same gun in either thigh (for example) and judge how much it subjectively hurts. Maybe also document the bruise severity as well the next day. While pain is of course subjective, I think it would be hard to refute such results since they are pretty much a test of exactly what we're after.

A messy proposition, but the shattered gelatin and highly visual nature of the hit result would be pretty cool. Shooting stuff that "does" something when hit is fun...

I did a couple more tests with that floral foam crap. Messy as hell.

The idea is to see if the different medium shows the same results. MadMax pointed out that many puttys are non-newtonian, something which didn't occur to me and was bugging me.

A few changes made:

1. Fired at 6" away instead of 2m
2. Foam has BDU material over it.
3. Still used .12, .20, .28 and .43 BBs. But this time only from the 1911 GBB on Duster and an APS2 bolt-action.
4. I tried a pure penetration test between .12g and .43g from an APS2 into the foam with no BDU over it. Just for fun.

Short story: Same results trend observed (the heavier the ammo, the harder the impact and deeper the penetration when fired from the same gun.)

It was interesting! Some lessons learned:

- Have a vacuum handy. It's messy.
- Vacuum also helps suck out the debris from the holes so you can see better.
- Not nearly as easy to measure this stuff with a depth gauge since it's so frangible/light/fragile. I gave up trying and just had to eyeball it.
- Shooting stuff is fun.

1911 on Duster from 6" away
http://unconventional-airsoft.com/gf...1911-Clean.jpg
Clear progression of wider/deeper/messier impact the heavier the BB gets. The BDU material is noticeably "dirtier" with foam-bits as the BBs get heavier.

APS2 from 6" away
http://unconventional-airsoft.com/gf...APS2-Clean.jpg
Same observations as above, but more pronounced.

Penetration test: APS2 firing .12g and .43g into bare foam from 6" away. Pictures are self-explanatory.

http://unconventional-airsoft.com/gf...tration-01.jpg
http://unconventional-airsoft.com/gf...tration-02.jpg
http://unconventional-airsoft.com/gf...tration-03.jpg
http://unconventional-airsoft.com/gf...tration-04.jpg
http://unconventional-airsoft.com/gf...tration-05.jpg
http://unconventional-airsoft.com/gf...tration-06.jpg

The .43g penetrated more than the .12g, but the difference was not as big as I thought it would have been. Hmmm!

Nice test.
What kind of foam is that?

I think we should move on to human test now. (o:

EDIT: It's floral arrangement foam.

Something just occurred to me -- I used the fishing line to cut up the APS2 result foam to bisect each impact crater!

Neat (and odd) that the difference between .12g and .20g is bigger than the difference between .20g and .28g, even though they are both .08g apart from one another.

You don't see it so much from this angle, but the width increase of the crater I think is more noticeable as you go .20 -> .28 -> .43 but the increased depth of penetration is harder to see.

http://www.unconventional-airsoft.co...APS2-split.jpg

Wow, excellent test. I think that clinches it for me. 0.12g pellets have significantly less damage potential than heavier ones.

However it does look like the 0.2g, 0.28g have nearly comparable damage potential to the 0.43g pellet which is a huge lot heavier. Are all those shots chronying in at equivalent energy? I'm wondering if the dinky 0.12g pellets are coming out with significantly less energy than the heavier ones indicating some sort of weight based limit where lighter pellets are not able to take on as much energy as heavier ones.

Now I'm curious to see how you can relate this to pain. FYI, the JOC club out of Calgary has a dedicated indoor facility and play a lot of CQB; they are required to use a MINIMUM of .20g BB's (.12's NOT allowed). I *believe* this is for pain reasons, but I'm not entirely sure. Maybe one them will chime in.

I think its more to do with the weight/speed curve that I was taking about earlier. The .43 does have more damage and slightly deeper craters than the .28, but for the .15g difference it is fun to see that my idea/theory that the reduction in speed due to the heavier weight does limit the addition of impact energy to the heavier rounds. I would be VERY interested to see this SAME test done at 10ft 20ft and 30ft ranges :D. To see if my theory that the farther the round gets the heavier ones are going to loose that impact energy sooner than the lighter rounds due to loss of speed. Though I suspect you would see the .28 and .43 catch up neck to neck at around the 50ft mark to have the same impact.

I am curious if there is an indication of the density of this foam that you are using, so that I can hit the local hobby supply shop and pick up some of the same stuff.

loss of speed is not loss of energy

Is it just me or what but the link is dead. I could view it on cached version but then most of the pics wouldn't load. Anyone knows?

Speed (along with mass) is directly proportional to energy imparted.

Think a bus hitting you at 1km/h is the same as 50 km/h? :p

E = 0.5[m][v^2]

Velocity actually changes energy of an object more than mass.

The only thing I was thinking is simply conditions and applications. A lot of guys use .20's for indoor winter gaming, simply because of the environment - no wind conditions, clear line of shot, inexpensive ammunition, etc.

I suspect that in indoor CQB environments using .20 and getting hit closer could hurt more than being hit by a .28 in an outdoor environment, simply from contact distances - ie: CQB tending to be closer.

Just anecdotally, I`ve been hit in the pinky (my least favorite place to take a shot) with .20 and .28 at about 15 feet, and I can say without a doubt the .28 had me hopping around and swearing like a mofo, whereas the .20 just stung. From that experience I`ve always thought heavier=hurtier.

Interesting thread, and kudo`s DonP, those are really creative testing methods.

Anyone knows what happened to cybersloth or the guy? I have just spent 8hrs reading and trying to understand the articles and I'm still only halfway through! Lots of useful info based on solid physics but a shame I couldn't read most of the graphs.

I think it's the 0.4g BBs storing more energy than the 0.12g ones, even though springs store the same amount of energy, the shape of the bbs, lack of air seal in the barrel, these all effect physics

I think it would be interesting to do the test with bb's from the same manufacturer to see if tolerances have a huge effect on the damage done. I say this because if you look at a bb like excel they have a much lower diameter then a normal bb which is why they are suggested when people have jamming issues. I also wonder how much hopup has an effect on these results. Even with the hopup fully off it still touches the round.