Lower Mainland Airsoft Group Forum

I’m trying to build a G&G pneumatic blowback up to 350FPS. A m100 spring gave me a consistent 300 FPS.

I dug through my random springs and found one that gave my Masada a consistent 350FPS and I put that spring into the MP5. After I put it all back together, its still shooting in the 295 300 FPS area.

Is it normal for pneumatic blowback rifles to lose on average 50FPS?

That sounds right I gained over 40 fps on my m4 and ak when I put in a new cylinder and lost the blow back.

Barrel length/Cylinder volume?

Now we have an idea that about 85% of air goes to push the bb out and 15% for the blowback

cook-off wrote:Barrel length/Cylinder volume?

its a proprietary full cylinder with a 7" barrel.

the front of the cylinder has a hole on top which redirects air into a secondary cylinder that does nothing but move the "bolt" back and forth, giving it a clack sound.

im going to put in a 380-390FPS spring, that should get me to where I wanna be.

could be the hole losing pressure on you?

but without knowing how much "working" cylinder volume you have, you might be pushing the BB down the barrel before you reach max piston speed, hence your cylinder is too much for a 7in or 130mm barrel, for that length barrel there should be a cylinder bleed hole around mid cylinder similar to a G36.

cook-off wrote:could be the hole losing pressure on you?

but without knowing how much "working" cylinder volume you have, you might be pushing the BB down the barrel before you reach max piston speed, hence your cylinder is too much for a 7in or 130mm barrel, for that length barrel there should be a cylinder bleed hole around mid cylinder similar to a G36.

I would most certainly agree. but since its a proprietary cylinder im pretty well hooped. Unless I wanna start drilling and blah blah blah. ill toss in a 380FPS spring and that should put me in the area of 340-350 and call her a day.

Or run a differant cylinder. If you can live with out the blowback its an easy fix.

its my cousins, he likes the blowback feature.... kids these days

Next thing you know they will be putting speakers on airsoft guns to make gun shot noises lol.