CA m249 fps drop
 

Hi everyone,

I have a Classic army M249 and last year before storing it for winter i had severe fps drop (normal was about 300fps and now it was shooting 90fps)

So for the last 2 week i tried to find the issue with no luck at all, but i did make some progress but now im completly out of idea so i need your help guys.

First i checked the gearbox, cleaned everything and did compression test. With that i now know my piston/cylinder/cylinder head assembly got perfect compression so no issue on that side and still shooting 100 fps.

Next i went to the hopup unit, felt i was loosing some air in the magwell when shooting. Changed the hop up rubber, added some teflon tape in between the rubber and the steel hopup unit. Put everything back together and no more leak in the magwell i now have around 160 fps.

Then when i did some chrono shot i saw that if i pulled the trigger enough to pre cock the spring but not shoot, wait a second, then shoot, i get my normal 300fps, checked the tappet plate spring and that little guy is still stiff too.

Thats where i am guys, need some opinion im all out of where to search for my problem

Thanks alot!
Ced1942

I got a couple of questions for you. When you cleaned everything does that include the inner barrel and the second one is how well does the air nozzle move

Yes i cleaned the inner barrel like 3 time to be sure.

And for the nozzle it moves fine, no feeding issue at all

Thanks!

is the hopup on?

I was doing my chrono with the hop up off to be sure it was no too tight

Thanks!

try turning the hopup on

Still getting low fps with the hop up turned on.

No other idea anyone? Kind of pissed off by this gun right now haha

Have you inspected the o-ring near the hop up?

The one that hold the dial ring? Its fine otherwise i dont
See any other oring