Feed-paths on bolt rifles

[Ghost Snake]

Originally Posted by Luckyorwhat

Seems like a trivial reason not to try. If accuracy is possible, I'm sure technology would move to catch up. Until then you could just hold-over.

Technology? What are you talking about? It's called basic physics. I'm not going to do the calculations, because honestly, I dont remember shit from high school. But if someone is 50 yards away from you, and you have to aim 12 feet over his head, its just not going to work. It has nothing to do with technology. To make this feasible, you would need a muzzle velocity in excess of 1000fps, minimum. If you can find people to play with you, then go for it.

[Luckyorwhat]

I appreciate the input, thanks. But maybe you could show me just a little bit of the math?

For instance, to get that high a MV you'd need a light projo, and if you've ever tried to crumple a piece of kleenex and throw it across the room, you see why that's no good. MV wouldn't trump retained velocity, in my opinion. Airsoft pellets right now have poor exterior ballsitics because the design is poor. Poor ballisic coefficients, secional densities, form factors, all of it. I'm not saying a better pellet would solve all the problems, but if it went straighter, and had 50% more range, wouldn't that be worthwhile?

[TheYellowDart]

A bullet shaped pellet will travel in a parabolic path because of gravity. I think Ghost Snake is just saying that the range would be poor for such a pellet because airsoft velocities are quite low. The pellet wouldn't fly much farther than current bb's do now with hop-up turned off. A good bullet shaped pellet would be more precise, hitting the same place each time, but would need to be lobbed at a target far away. As the distance of the target changes, you would have to aim higher or lower. This won't be as a big of a problem if the gun has a good graduated sight. Hop-up makes bb's fly in a straight line, not in a parabolic curve, so you can just point and shoot. The back spin gives the bb lift to fight off the effects of gravity so the bb stays airborne longer.

If you could some how give give a bullet shaped pellet lifting properties, that would be an interesting idea.

[Ghost Snake]

I'll try to do the math, but give me a while, because like I said, I dont remember shit from high school. To be useful, I still think you'd need a velocity exceeding 1000fps. And to retain most of this velocity, you'd need a fairly heavy pellet. Heavy pellet + high velocity = very painful. A .177 pellet gun pellet weighs 0.51 grams. A 6mm airsoft bb (about .243) weighs .20g-.36g generally. Therefore, an airsoft bb has less weight and more surface area. So it's pretty safe to assume that an airsoft bb has a greater drag coefficient. Even if you designed a better bb with less drag, at 1000fps, it would have to be very light to still be safe, and very light means it wont go very far. You just cannot design it so that you have the range while keeping it safe. I hope that makes some sense. To sum it up briefly:

-to get the range, you would need a high velocity and a heavy bb, this would make it very unsafe, as well as classify it as a real firearm
-to make it safe, you would need a low velocity, or a very light bb. Whichever one you choose, you will not get the range

Something to think about though. If it was possible to make a rifled airsoft gun that had range and was safe to play with, it would have been made a long time ago. There is a reason why all the companies have gone with hop up to get range. And yes, I know this thread is all about a rifled airsoft gun, but it is by no means safe to play with.

[Ghost Snake]

Originally Posted by Myoga

If you could some how give give a bullet shaped pellet lifting properties, that would be an interesting idea.

To get this to work, the bullet wouldnt be able to have any spin. Therefore you would lose all accuracy.

[Ghost Snake]

Alright, here we go. Who needs to do math when you can use an online ballistics calculator. Plus, this way I can use the drag coefficient as well.

-velocity 1000fps
-bullet weight 5 grains aka 0.33g, a common airsoft sniping bb weight
-range is in yards
-drop is in inches
-ToF = time of flight
-and energy is in ft lbs.

This is what I feel would be acceptable for gaming. At 100 yards, it has lost almost all energy, so this is about the maximum range. A 100 yard max range is decent for games. You would rarely shoot farther than that. At 100 yards, the drop is 50 inches. A high end Schmidt & Bender scope will give you a 56 MOA adjustment, so if zeroed properly, you would just be within the scopes range. But, I'm guessing most people wouldnt take the time to adjust the scope that many clicks. It wouldn't be that hard to just guesstimate 4 feet above the target and shoot. So, these ballistics sound pretty good, except...... muzzle energy is 11.2 ft lbs. which is over 15 joules. Just a little over field limits :-D 1.5-2 joules is a common outdoor limit. This would also make it a firearm, and would have to be licensed. It would also then be illegal to point at a person.

So there you go, to get an acceptable trajectory, the energy would just be way too high (and illegal).

If anyone needs clarification on anything, just ask.

[Greylocks]

Use google. The word you are asking us to spoonfeed you is: ballistics.

[Luckyorwhat]

Thanks a million Ghost Snake, and I'll be your friend for life if you share the location of that ballistics calculator, I like the features it has! much fancier than the junk I've been using. (unless you took a screenshot of a purchased program). I'll give this address I've got on energy conversions, in exchange:
http://www.ajdesigner.com/phpenergyk...ation_mass.php

And I'd really really like to see the work on the BC calculation, what shape is it based on, etc?


"Ke=5.7joule, v=152meter/second, mass (m)=7.6146505031079 grain; 0.49342105263158gram"

I'd agree that safety is the top concern, and that velocity is limited, as is energy. But I believe there is some wiggle room that satisfies ballistics, safety and legality. Just need to find it!

For instance, retained velocity is based on the ballistic coefficient. It's possible you can get better retained velocity by increasing mass and reducing velocity proportionally. On top of that, there's form factor, the air resistance of the shape.



Also thank-you Myoga, I did understand better when you explained it.

[Ghost Snake]

Well you know, it was pretty hard to find. I mean, it was the first result when I typed in "ballistic calculator" on google. :wink:
http://www.handloads.com/calc/

When using the coefficient calculator, it doesnt accept bullet weights under 10 grains. So if you want the coefficient for a 5 grain bullet, do the calculation for a 10 grain, and then divide by 2. I did my calculations with a bullet diameter of .243 (roughly 6mm), weight of 10 grains, and I used HP as the bullet shape. This gave a coefficient of 0.021. My calculations were based on a 5 grain projectile, so 0.021 / 2 is 0.011. I used the HP shape because it was the closest to a pellet gun pellet.

A "blade bullet" though would be closer to the coefficient achieved by a boattail, maybe even a little better? Speaking of blade bullets, I wasnt able to find out for sure, but one source said that they were .34g. A blade bullet could potentially give you a coefficient somewhere around 0.025. But thats just a guess.

I spent over an hour trying to find a useable combination of bullet weight, velocity, etc. but I just couldnt get the energy low enough. I dont think a bullet weight under 0.34g (5 grains) would be stable. Leaving the coefficient and range out of it for a second. The max velocity a 0.34g bullet could be, before reaching the legal limit is 602fps. This wont give you very good range no matter what the coefficient. But keep in mind that even though it would be legal, there is no way you would want to play with that. If you are very careful about where you shoot a person, you could maybe get away with 2.5 joules, but even that is pushing it.

So, in conclusion, I personally dont think that rifled barrels and bullet shaped projectiles will ever be used in airsoft. And after using that calculator, I have also come to the conclusion that while the Asahi M700/M40 guns were cool, they were completely impractical for use in a game, simply because to be effective, the energy would have been way too high.

Another link that may help you is the fps/energy calculator on arnies. http://www.arniesairsoft.co.uk/?filn...s/fps_calc.htm

EDIT: Now that I actually look it up, 6mm is more like 0.236". Not that that would really affect the final results though.

[ToRN]

well, it 'is' possible.

There is .22lr subsonic ammo that shoots at ~550fps at muzzle.
there is not as drastic a difference as you think there is between 425 (common bolt action limit in ontaio, and 550.

That said, good luck getting the gun to work this way, it would envolve lots of calculations and intensive engineering work.

[Ghost Snake]

Originally Posted by ToRN

well, it 'is' possible.

There is .22lr subsonic ammo that shoots at ~550fps at muzzle.
there is not as drastic a difference as you think there is between 425 (common bolt action limit in ontaio, and 550.

That said, good luck getting the gun to work this way, it would envolve lots of calculations and intensive engineering work.

No, its not possible. Fps isnt everything, far from it. So it shoots 550, big deal. What does the bullet weigh? A quick google search shows that subsonic .22 lr ammo weighs between 38 grains and 60 grains. Even at the lowest, 38 grains, that is still 33 joules of energy at 550 fps. Do you normally play at those kind of levels?

[Mysteryfish]

From what I remember (for clarification) the Asashi was never meant to skirmish.

It was for Japanese gun enthusiasts who (due to Japan's laws) cannot own the real rifle.

It was quite powerful, and even had aftermarket upgrades for the shells to get even more power (the shells were pumped up by a special hand pump to high pressure, to propel the rounds)

If I'm not totally mistaken, it was more for joy of ownership and for the pleasure of using a fully functional bolt action rifle that required no actual bullets.

It was a dead on replica, down to the last detail, and was so similar in function to a real rifle, that people were fitting .22 calibre barrels into them and using them to fire real ammunition.



Thus, the rifles were re-called and destroyed, with a few individuals who never bothered documenting their ownership (I think it had something to do with warranties), not being on the list for reposession.

So, there are a handful of the rifles floating around out there.

All this information came from some website that I can't remember the address for off the top of my head, but searching for "asahi rifle" and "holy grail" in the same search topic should find you the page :grin:

And yes, Ghost snake is right, FPS isn't everything, because if my 12 ft*lbs pellet rifle blasts holes in half inch plywood, 33 ft*lbs is going to wreck some tissue for sure.

For the record, the pellet rifle is slinging pellets at close to 700 FPS, which is somewhat lower than the .22 subsonic's 550 8)

Lots of factors. Mmm, factors.

[Luckyorwhat]

Ghost Snake, thanks for the link, but eh-he I was tired and mis-read a couple of the boxes. Wishful thinking. I use the Eskimo.com stuff, it works, and what's missing I guesstimate and calculate.

But working with numbers for lighter and slower pellets, with a BC of only 0.15 you can get .30grn 500fps projectiles out to 50m with a max trajectory height of 4-5 inches at 25m, and still only dropping 12 inches by 70-75 meters. For reference, urban light posts seem to be placed about 50-60 meters apart on slow streets, 100 on faster streets. Of course, by 100m you're aiming 40 inches higher, but if the bullet goes straight and the wind is still, it just needs range estimation and skill to make hits.

For the blade bullet, I'm not sure about the design. I'd figured a design with 2 contact points, one on the head and one on the fins. Oh well, article says they were good to 100m.
http://www.airsoftplayers.com/m40a1/Ammo.jpg

[ToRN]

Yes, fps isn't everything, and maybe the .22 subsonic was a bad example, but neither is bullet wheight. If bullet wheight had that much of an impact, how then can you explain bb guns, and pellet guns, that fire under 495, with quite decent accuracy, out to 100yds and more? And before you say it, yes, I know that steel bbs and lead pellets wheigh more than a bb, but if it can be engineered for them, it's not so far a strech of the imagination for the same to be done for airsoft bbs.

[Mysteryfish]

You're talking about a different point than he is.

You're arguing about flight trajectory and projectile stability.

He was merely trying to point out that muzzle energy and energy at impact are largely dependant on projectile mass. (with regards to safety and what projectile properties you would require to get a realistically useful trajectory without hop-up)

But even still, projectile mass plays a large part anyways, because of inertia. Even a well engineered shaped projectile that is lightweight is subject to being thrown off course or tumbling much faster than a hevier projectile **OF THE SAME SHAPE**, since it simply takes less to alter it's course.

** (i forgot to add this important point)