FPS issues?

[_Firebird_]

I just recently put a m120 spring in my gun. I've done this before with out any problems before. I chronoed the gun to day and it's shooting at 173 FPS and it has an m120 spring in it. I'm not sure what I did, so what could be causing the sudden drop in FPS?

[Green Listerine]

What else did you do? Sounds like you have a massive air leak, or maybe you put the cylinder in backwards

[_Firebird_]

That's all I did. I only changed the spring, and I'm positive I didn't put the cylinder in backwards. Would it have something to do with the air nozzle maybe?

[Green Listerine]

It could be. I would check airseal between the air nozzle and hop up unit first. If you dont find anything, just take the gun apart and check all the airseal components. It's hard to say with things like this because there are so many things that could be wrong and i don't have the gun in front of me

Edit: are the shots consistently under 200fps?

[_Firebird_]

It could be. I would check airseal between the air nozzle and hop up unit first. If you dont find anything, just take the gun apart and check all the airseal components. It's hard to say with things like this because there are so many things that could be wrong and i don't have the gun in front of me

Edit: are the shots consistently under 200fps?

Alright, well thanks for the help. I'll keep playing around with it to see what I can find.

[Major payne]

Check your O-ring on your piston, I had a bad O-ring drop my fps by 150. I usually take my piston, piston head, cylinder and cylinder head out and test the compression under water (in my sink) by plugging the cylinder head nozzle with my finger and pushing on the piston. Most O-rings for AEGs are like a #14 in size. Make sure your hop-up bucking is in good shape too.

[_Firebird_]

Check your O-ring on your piston, I had a bad O-ring drop my fps by 150. I usually take my piston, piston head, cylinder and cylinder head out and test the compression under water (in my sink) by plugging the cylinder head nozzle with my finger and pushing on the piston. Most O-rings for AEGs are like a #14 in size. Make sure your hop-up bucking is in good shape too.

I opened the gearbox so I could check the compression and what I came to find was that the first two teeth on the piston had cracked right off the piston. Would that be my problem or does it still sound like a compression problem?

[bailey5671]

Check your O-ring on your piston, I had a bad O-ring drop my fps by 150. I usually take my piston, piston head, cylinder and cylinder head out and test the compression under water (in my sink) by plugging the cylinder head nozzle with my finger and pushing on the piston. Most O-rings for AEGs are like a #14 in size. Make sure your hop-up bucking is in good shape too.

I opened the gearbox so I could check the compression and what I came to find was that the first two teeth on the piston had cracked right off the piston. Would that be my problem or does it still sound like a compression problem?

If its the first two teeth in the front of the piston then it may explain the fps drop. In any case you might want to get a new piston.

[Major payne]

The teeth being cracked off the piston would definitely cause loss of power like that. Definitely replace the piston, and check the other areas off compression, the O-ring, Hop-Up, air nozzle and the cylinder head. Having two teeth break on the piston is just like short stroking a gearbox. When you short stroke you gain roughly 1 bps per tooth you take off (accept that you take it off the sector gear) so your piston will not be going back all of the way because there are no teeth to get it there so it results in a shorter stroke and faster cycle and a drop in FPS.

[_Firebird_]

I replaced the piston and the air nozzle. It seems like the gun is shooting a lot better.

[Major payne]

Good, I am very glad to hear that. I just went through a rough patch with my KWA and it is quite depressing when a gun is not functioning properly