[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.