random 100fps drop off on some shots
 

I have an Ares stoner LMG. Shoots ok except every 4th shot or so loses 100fps for some reason. Normally shooting 380-390 fps with the odd shot doing 270ish...

The air system has been tested and is solid.


Anyone have any ideas?

Hopup rubber wearing?

BB's mixed with heavier ones?

could be your BBs pressuring the air nozzle, I had that issue a while back where someone would hit the auto feed and the gun would lose FPS for the first few rounds

tappet plate may be sticky

could the ammo you're using

could be the hopup

could be a piston head seal problem

whens the last time you cleaned the barrel?

and is this a winter problem, or does it do this indoors?

The gun is basically new. A few thousand rounds put through it (very easy to do with an LMG!) and never gamed.

It has had a shim and grease, airseal check and new pommy barrel put in. Still has the drop off issue.