M4A1 Low FPS After Upgrades

[Stealth]

Originally Posted by Remylebeau

Question in regards to cylinders -

Say your inner barrel is 300mm - do you then use the type 2 (200mm to 300mm) or the type 1 (300mm - 450mm)?

Depends on how strong your spring is. If under 400fps, I would use the Type2, if over, then Type 1.

The rationale beyond cylinder volume matching is that you want the BB to only start moving down the barrel when the piston is near its maximum velocity. If using a soft spring and a Type 1 cylinder, because the piston creates a seal much earlier in the stroke, the BB may leave the barrel before the piston is at its maximum velocity. If you shift to a Type 2 cylinder, it gives sufficient time for the piston to accelerate before creating a seal.

[lurkingknight]

sorbo does reduce the volume so you could see 10 or so fps loss with just a 3/16th pad, depending on cylinder volume.

I had this cylinder head and a type 2 (meant for the 247 length barrel) in the gun and without it the gun shot 400... with that sorbo in the short cylinder, the gun was doing about 150 really not enough air. if you are within 10 of original with your sorbo, that's where you should be.

My p90 dropped about 8 fps with the sorbo install. 247mm 6.03mm with a type 2 cylinder.

Originally Posted by Bar1975

Well i have an update.

I've removed the Sorbo and put a new one back on. I removed the stock cylinder head rubber so the new Sorbo is directly onto the cylinder now.

I'm in the ball park of 320-330FPS using .25g and upwards of 370-380FPS for .2g (still maintaining a 26-28RPS ROF)

i guess that's everything i can do for now. Would still like to have this gun back up to it's original FPS of 390ish (.2g) though