M4 fps issue

[Mongrol]

I have a 2GX KWA M4 that has a weird fps issue. I have a 400 fps spring in it (stock spring) and have a super nice seal. I cant push the piston at all past the port in my cylinder. (this is while the gear box is apart of course) so it seems my seal is great. But when i put it back together im only shooting 270 fps. The only thing i can think of is that i have a stock G&G bucking that might not be getting a good seal OR something is happening when i put the gearbox back together that is causeing a leak.

Any ideas?

[pseudoanimosity]

Before you open it up again, inspect the air nozzle/hop up interface, there might be something funky going on there. Another option is to wrap the front of your hop up chamber (where the inner barrel meets the hop up chamber, and over the barrel clip) in teflon tape to make it air tight.

[Mongrol]

gracias, shall try it and see how things go

[GaBoOwnz]

You checked to make sure the bucking wasn't ripped or seated incorrectly?

[Jester316]

Components affecting airseal listed in order from muzzle to stock:

barrel, hop up rubber, hop up chamber, air nozzle, cylinder head, piston head, piston head o-ring, cylinder

Anyone of those could be your issue. While all individuals might work great separately, when combined they can all create havoc. You have to check each piece individually both as individuals, and as part of the system to nail it down.

[Jewish Ninja]

Also, it depends on your mags. I've seen KWA's shoot lower with certain brands of mags.Other things that can effect your FPS is how high the hop-up is dialed and the brand/weight of BBs. Also, in this time of year, you can expect the cold to cause it to shoot low (assuming the gun is cold as well).

[Switchback]

High magazine spring tension separating 2 piece hop up unit?