Is it possible? 550FPS+? On a KJW M700...

[Gryphon]

Yep. According to the regulations and Arnie's FPS/Joule calculator, we can push 785 fps with a 0.20g before it becomes a firearm.

[Kid]

Totally off topic, but I don't want to gravedig and the info has been given, may as well.

CND_Stalker,
You've mentioned that you have mags with 30 rnds?
Which is that? Would that happen to be the long Tanaka mags?

There were conflicting reports on that, so I was wondering about that.

Or would that be the custom one MadMax was working on...?


You had mentioned before that you had planned to do some modifications in another thread. Have you had any more progress on those? Any recommendations for the ASC comunity?

[Mantelope]

Originally Posted by CDN_Stalker

I chronied, WITH 0.20g BBs (my point to dispell 700+fps with 0.36g BBs

Guns don't usually translate perfectly between different BB weights even if you're using the proper math. This is especially true with gas guns; a heavier BB means it will be in the barrel for a longer period of time, which means it will be accelerated for a longer period of time. This is why you get such good performance with heavy BBs in your Glock.

[MadMax]

Definitely a salient point with gas guns. It appears that AEGs and other spring guns are pretty much constant energy guns in that the muzzle energy is consistent dispite changing pellet weight. However, many gas guns do not exhibit constant energy with different bb mass.

I suspect that when lighter pellets are used, the breech pressure drops because the pellet accelerates down the barrel fast. The rapid expansion of volume behind the pellet results in higher pressure drops in restrictions like in the fire valve or other gas flow paths which causes lower breech pressure.

Reduced breech pressure means less force acting on the pellet (pressure x area) which means less work done accelerating the pellet (reduced force x distance).

This doesn't appear to be the case with AEGs which have very simple gas flow paths. The bore of the nozzle and cylinder centre port is not much smaller than the barrel. The reaction force of accelerating the pellet appears to be the dominant restriction.

Gas guns have more convoluted flow paths and the fire valve takes a little time to fully open. A heavier pellet presents a more significant flow restriction than a lighter one (relative to the flow resistances) so it can absorb more work energy.

In essence, I am conjecturing that an ASG can be approximated as a series of gas flow resistances analogous to electrical resistors in a circuit.

The flow restrictions of various orifaces and the barrel represent a chain of smallish resistances which are constant. They will incur a higher pressure drop at higher flow rates. Similarly a resistor incurs a higher voltage drop at higher currents (Ohms law: V=IR)

However, the pellet represents a wierd resistance. It's resistance varies with time. The pressure drop across a pellet (between breech side and front side) is the difference in breech pressure and atmospheric pressure. The odd thing is the resultant flow rate is dependant on how fast the pellet is moving. A faster pellet ends up having a higher rate of volume change behind the pellet. In a sense, the pellet starts out at a high flow resistance which decays to a lower flow resistance by the time it's screaming out the barrel.

If the constant resistance of the flow path upstream of the pellet is very small, nearly all of the pressure drop occurs across the pellet so different weight pellets will have the same work done on them for the same fixed barrel length ~ constant muzzle energy despite different pellet weights.

If the constant resistance of the upstream flow path is not negligible, then the pressure drop across the various resistances in the flow path will reduce the pressure acting on the pellet so lighter pellets have less work done on them and therefore have higher speed (higher flow rate), but less muzzle energy because the average force acting over the barrel length is less.

Now I have to put my head back together because my brain just exploded.

[MadMax]

In response to the original post, it is quite possible that a KJW M700 on ebay pushes well over 500fps w' 0.2g pellets:

http://www.airsoftcanada.com/showthread.php?t=14509

[KraziAzn]

Thank You. Wow that was one hell of a thread. =D

[CDN_Stalker]

Originally Posted by Kid

Totally off topic, but I don't want to gravedig and the info has been given, may as well.

CND_Stalker,
You've mentioned that you have mags with 30 rnds?
Which is that? Would that happen to be the long Tanaka mags?

There were conflicting reports on that, so I was wondering about that.

Or would that be the custom one MadMax was working on...?


You had mentioned before that you had planned to do some modifications in another thread. Have you had any more progress on those? Any recommendations for the ASC comunity?

I only own 10rd standard mags in my M700, although a Tanaka 30rd mag would be a neat change to make.

Only mods I did and mentioend on my M700 were down withint a couple days of receiving it, cut the striker spring down by two coils to reduce the amount of force it releases gas at, making it release gas more consistant; and remove the stock to barrel support to let the outer (and result inner) barrels lie as they want to. Truns out the three I ordered (two are in the hands of team mates, same thing with theirs) is the outer barrel wants to lie to the left a bit, meaning when we received them, the inner barrels were slightly curved due to the support. Used to get 10shot CD sized groups at 30ft the first few weeks I had it, things worked in well and now I get consistant dime sized groups with it at 30ft with whatever ammo I use (Straights are not as good though unless washed). Only thing I did mod was to install a G&G Striker Spring for the Tanaka M24 and M700, found I didn't like it (have to NIB ones for sale though) as it made the power go up even MORE from stock, increased bolt pull and trigger pull as well.

One thing I found is tha the KJW M700 needs to have a dry swab run through it every 30 or so shots to keep the consistancy at it's best, otherwise flyers start occuring.