Warning for KJW M700 users and game orgs

[MadMax]

This is a safety related warning for game organizers and KJW M700 users. I have just chronied a KJW M700 propelled by propane at 26.5C and recorded alarmingly high results:

Measurements in fps shot 10s apart

BBs propelled by propane
0.43g Straight: 548, 533, 529, 524
0.36g Straight: 538, 548, 538, 540
0.25g Guarder: 633, 594, 586, 585

KJW M700 users should not be using propane to propel their rifles especially with even hotter outdoor temperatures to come. Game organizers should be aware that gas rifles chrony tested with duster can easily be refilled with propane after an initial chrony test.

BBs propelled by HFC134a
0.43g Straight: 386, 375, 362, 373
0.36g Straight: 428, 417, 381, 393
0.25g Guarder: 461, 428, 425, 408

When I first chronied a M700 at Grim Fandango's house, we shot 0.2g bbs propelled by propane in his rather cool basement. Shot velocity was typically around 575fps. While this is quite hot for a stock sniper rifle, it is not uncommon for significantly upgraded rifles to be fielded with this kind of power.

In most airsoft guns, using a much heavier bb (0.43g vs 0.2g) typically results in a significant drop in muzzle velocity. Velocity drop is roughly related to the constant energy output of a particular gun.

However, under typical summer gaming conditions (i.e. 26.5C), muzzle velocity is barely diminished with the usage of heavier bbs with the KJW M700. It is possible that some sort of flow restriction in the pneumatics of the KJW M700 is setting the upper limit of projectile speed instead of projectile mass. Regardless of the cause, a propane propelled KJW M700 is capable of very high muzzle velocity with heavy sniper rounds.

Food for thought:

A 0.177cal pellet weighs 7.5 grains which is equal to 0.48g. Therefore a 0.43g Straight brand bb has nearly the same muzzle energy as a 0.177cal lead pellet when both are fired at 500fps.

[FOX_111]

8-O tanx for the warning!

[Suspect187]

MarpatMarps and I were shooting his M700 in my basement. We didn't have a chronograph. Thx for the info

[Ghost Snake]

Ouch. 548 fps with a .43g bb is not something I want hitting me in the forehead.

[Sadiztix]

is this that carbine version of the mk1 ?
cause that motherfucker runs hotter than hell out of the box
in the 500 ish area with propane

[Tankdude]

548 fps with .43 is 5.992 joules. mmmmmmmmmmm ya, screw that.

[Greylocks]

Most places I know test all guns with .20, so just using a fairly light BB and a chrony would take care of that risk.
Above the local field limits means no game.
I wont go into the legalities.

[Primus]

"Hi I like to post to just hear myself talk..."

[Lisa]

Originally Posted by Primus

"Hi I like to post to just hear myself talk..."

Damn, and I hadn't even posted yet :lol:

Greylocks. with many sites the limit is 450-500 with .36 PROVIDING you have taken and passed the sniper clinic by Sha Do. I won't get into the specifics of the course (that's best left for Sha Do) but from the legality/criminal aspect it's joules first then FPS. I'm sure you can do the math. That being said, the readings that Carl's gotten are something to pay attention to. I wonder how duster will do at the height of summer when we have 40+ c temps.

Should be ok so long as duster is used.
Problem I noticed, is the gun isnt overly accurate, and a tightbore would be needed...but that would again, boost your FPS.

that cheap duster in the blue can should keep the gun below 450.

We had one out at the LZ. Was hotter then hell. Engagment range is huge with these guns.

I rember there being some test comparing .20g to .25g bbs against eachother. It showed velocitys at differnt distances. Id like to see what the FPS and impact energy there would be at...oh, i donno, 100 feet, 200 feet and so on.

yah, +600 fps is brutal, but Id like to know what it would be like getting hit at a distance.

with AEGs and sniper rifles beging seperated by only 50fps(400 to 450), the sniper rifle is usless. Having a rifle that actually shoots 200-300 feet would be nice to see on the field.
yah yah yah, I hear yah greylocks. but id like to see the tests.

I volunteer to get hit at distances by the M700 on propane

[Donor]

Originally Posted by Droc

...I volunteer to get hit at distances by the M700 on propane

I want a video of this :-P

[CDN_Stalker]

I did my testing as well, and came up with similar numbers as Max did. 134a seems to be the safest to use by far. I found that with the two mods I did (free float the barrel to straighten out the inner barrel, and cut two wires off the end of the hammer spring to reduce the amount of gas expelled per shot) I get more consistant shots, and a LOT better accuracy (how about a ~1.25" hole at 30ft?) . Numbers I got with shooting .2g BBs and 134a showed the first initial shot was 461fps (EDIT: Mistyped the number, fixed now), but all others from the mag were under 450fps, ranging from 435 to 444fps.

If that seems to high for some fields use (aka. those with 400fps max for bolt action) then take a trip to Staples and buy the Kennsington's duster, it's the diflouroethane crap instead of tetraflouroethane (134a). It should get you around 400fps or under.

As for it needing a tightbore, I'm not overly sure. See, I constantly clean my barrels the exact same way each time, take a .22cal patch, fold it in three, put it in my rod, roll it around, drop of oil on each side, then place it in my barrel. My M24 has a 6.03mm barrel, yet it has less resistance than either the M700 or my KSC G19. Common sense says if the inner barrel offers more resistance (tighter fit) than other barrels, including tightbores..................?

And to Droc.................. Go long buddy!!!

[manchovie]

if the ratio of intelligent to retarded posts in this thread is something like the ratio of intelligent to retarded m700 owners, we're all fucked.

tanaka m700's (on which the kjw was based) in all their different models were around for a rather long time and were always hot on propane. the reason this issue didnt come up before was that, generally speaking, tanaka owners usually had a fair amount of experience sniping. m700's are not beginner's guns, gaming one is rather challenging, 10bb's per mag, varying consistency in gas pressure (having to do a ranging shot every time you reload and setting the hopup by feel) keeping minimum engagement ranges in mind and high cost of a tanaka all factor in to this. it used to take a certain amount of devotion to be an m700 user.

now that the cost factor has gone out the window, and the fact that you dont need to upgrade this gun to get the power up has probably made the kj m700 a VERY tempting gun for newbs to pick up as their first airsoft gun, and that's a scary ass thought.

i dont have a problem with experienced snipers using a hot gun (600 or so fps with .2's) but with regular snipers (APS, VSR...) the velocity with sniper weight bb's actually goes down like it should. what is with the m700 keeping the high velocities? the actual impact energy goes up drastically with the heavier bb's.

either way, thank god you did these chrony tests. now people are nice and shit scared of those things and hopefully players will keep an eye on things.

Originally Posted by Tankdude

548 fps with .43 is 5.992 joules. mmmmmmmmmmm ya, screw that.

at point blank

its not a CQB weapon

I figure that at 200 feet, that 600fps M700 will feel like a springer from 20 feet.

Personally, I got no problem with a 600fps rifle so long as they dont engage within 100 feet or so. In that situation, its up to the field admin to see who is responsible to fallow engagment ranges with a gun that strong. No different then the admin making sure people dont take upgraded AEGs in a CQB house.

I think the sniper role is very important, but when snipers and AEG are seperated by 50fps...common, thats crazy. Lets allow the snipers to be snipers.

But before we do anything, lets see what the M700 can do. Lets hit goggles with the M700 on propane. I volunteer to wear by camo and be hit at differnt distances with the M700 on propane.

Before we all run for the hills when someone says 500fps, lets look at it. I been hit with 500fps at 60 feet. Ill tell you, a GBB in CQB is far worse. Lets see how it does with goggles. I been hit by 400fps, and 450fps, and I cant tell the difference. 600fps at 250 feet is nothing. I havent done the math, but im sure at a distance, its not that fast.

[MadMax]

Originally Posted by Greylocks

Most places I know test all guns with .20, so just using a fairly light BB and a chrony would take care of that risk.
Above the local field limits means no game.
I wont go into the legalities.

I think game orgs have to figure out what they're willing to accept in terms of muzzle velocity and bb weight. The traditional fps limit attached to a 0.2g bb projectile mass doesn't really mean anything with gas guns which do not output constant muzzle energy.

A 0.43g bb carries roughly 30% more muzzle energy than a 0.25g bbs propelled (HFC134a). I submit that a muzzle velocity limit attached to 0.2g bb mass is not a very useful definition for safe shooting.

I think if we want to set useful sniping limitations, we should make actual fps measurements at various ranges to determine what kinds of speeds with sniper weight rounds and connect them to muzzle velocity.

Define a minimum engagement range that players can perceive without rangefinding tools. We all actually have different concepts of distance so we should really measure it out on a field and get a look at what 50' actually looks like (I'm just using 50' for example).

Reduce that distance by a safety factor (say 30%) and set up chrono at that range (call it "safe range"). Measure ranged pellet velocity with respect to muzzle velocity and pellet mass.

Unfortunately at some point, some sort of pain test is required to determine a maximum allowable impact energy at the reduced min' engagement range. We seem to be willing to accept that getting smacked by a 400fps pellet at a very close range is acceptably safe. This can start a fist fight, but it isn't directly dangerous. Perhaps comparing penetration depth into a piece of soft white foam could provide a good impact energy assessment without having to give guinea pigs implants. Blast a 0.2g 400fps bb into foam and measure the penetration depth. Fire sniper weight bbs into the same foam at varying muzzle velocities to determine the speed where equivalent penetration depth is acheived. Hopefully a direct correlation to muzzle energy will arise (1/2mV^2) which would facilitate future experimentation.

When you get sniper weight bbs embedded similarly to 0.2g pellets at 400fps, you'll have also measured the impact energy which can be used to determine the acceptable velocity for an impact at the safe range. You could also shoot at the foam at the safe range and skip the ranged chrony measurements. Measure muzzle velocity to correlate penetration depth at the safe range with respect to muzzle velocity.