An example I experienced that shows roughly what Illusion said about gas guns is my KSC G19. It's upgraded, only fps enhancing thing is the tightbore (I do believe the mass of the metal slide and stiffer recoil spring causes a delay in the blowback, therefore letting the gas expand a bit longer, increasing the fps............. which seems to be the case in the KSC Mk23 recoil spring I rebuilt last night, differently, it has a lot more resistance now so the action is snappier, and seems to shoot harder as well) and I chronied it one day at 341fps with 0.20g BBs. I got that same reading both shots I took. Then I chronied it next shot with a 0.43g BB (what I was using full time back then) and I got about 265fps. I told Brian, he explained the increase in gas expansion thing he pointed out above, and figured that for the gas expansion with the heavier BB, it'd be roughly about a 0.20g BB coming out aroud 380fps.
Here's an interesting bit of info related to above. I study a lot of airsoft ballistics, largely in the area of sniper rifles. Numerous times when I chrony my or others guns with 0.20g BBs, I might follow up with a 0.36g if that's what the user wants to use. I continuously find a 100fps difference in velocity between the two. So if the rifle shot 341fps using a .20g, the 0.36g BB would sit around 240fps, and a 0.43g BB might be ~40fps lower in the same gun. With my G19, I only had a loss of ~75fps using the 0.43g, around half of what fps droppage I'd get with a constant air gun.
Last edited by CDN_Stalker; July 10th, 2007 at 11:23..