Magpul sentry varying fps after opening gearbox

[Chrisjames91]

As a few of you may know iv installed an ascu mosfet into my g&p magpul sentry. I love the thing now its all done. The trigger response is immense and you can double tap so quikly the enemy wpnt stand a chance. The burst feature is a beaut aswell :p

Anyway.... Me and a freind have installed it ourselves. He has taken apart a few gearboxes before but i havnt but we both kind of know our way around one. Hes a mechanic and im an electician so together we have managed to do it. But now its all back together the fps is not very consistant. Before it was firing with a differance of 5 at the most but now its usualy 20-30 or even 50 on some shots. So whats happend?

When i opened the gb up there wasnt much grease on the gears so i ordered a gearbox grease pack from zero one so i can grease the gears and the cylinder o ring incase its either of them. But i didnt take the cylinder head out of the cylinder at all so i doubt it could be that. But il grease it all up just incase.

Iv easily had 20,000 rounds through the gun and never had it serviced so could this be why? Iv got to open up the gb to grease it all up and change the spring so i could do a mini service myself then?

But any ideas on what else it could be?

Thanks
Chris

[Basketash]

Re: Magpul sentry varying fps after opening gearbox

First thing I'd do is check the compression on the seal on your cylinder by simply covering your nozzle and pushing the piston down manually it's should not allow you to push It in and if it does I'd recommend a marui piston I think there about £10. Normally this will solve the problem as it sounds the seals are wearing on one side allowing piston wobble