fathom1001 Posted January 21, 2010 Report Share Posted January 21, 2010 OK, so I've had an A&K M249 Para that I got a while back from new when Airsoft Scotland got their second batch in originally. It had sat at my house for a while and I decided to change the spring down to something more reasonable than the stock one, I also made the hop a bit more effective by adding a bit of soft rubber tube under it. After I'd done this I tested it and the fps was all over the place, originally it wasnt the best but it got a lot worse. I immediately undid what I'd just done but with no change (the fps was up due to the more powerful original spring again but still not consistent). I checked all seals and made sure they were greased OK and eventually ended up replacing the cylinder, cylinder head and piston head (The original A&K piston head is a bit longer than the replacement so I also tried just replacing the o-ring on the original piston head). This made no difference, so I'm a bit puzzled. I also replaced the bearings in the gearbox, but I don't see how that would make any difference. I haven't looked at the gun in some time, its just been sat at home, I'm now at uni and would quite like to sell it but I thought I'd give fixing it a final try before I let someone else give it a shot. Link to post Share on other sites
Tom Andrews Posted January 24, 2010 Report Share Posted January 24, 2010 On the barrel is a spring and a sliding ali collar, is this still in place? Its meant to push the hop unit up against the gearbox and give the nozzle/hop rubber a good seal. Link to post Share on other sites
Docv400 Posted January 24, 2010 Report Share Posted January 24, 2010 Sounds familiar... M249 hop sealing issues... What was the fps like when you first got it? As for swapping springs, I know it's a piece of cake on them but the spring guide carrier can be modded so it has two positions, see post #25 on the topic I linked to. Link to post Share on other sites
thewallhitme Posted January 24, 2010 Report Share Posted January 24, 2010 On the barrel is a spring and a sliding ali collar, is this still in place? Its meant to push the hop unit up against the gearbox and give the nozzle/hop rubber a good seal. about this: i replaced my hopup chamber, but i forgot which order these parts go on. there is one quite chunky silvery ring, one smaller one and a spring. could youtell me which way they all go? Link to post Share on other sites
Docv400 Posted January 24, 2010 Report Share Posted January 24, 2010 The flat brass ring slides on first, once the inner barrel is in the hop unit, and fills the gap between them. It has a gap in it because of the grubscrew mod I did to the hop unit. Then the spring goes on, followed by the alloy collar, the thin end of which goes to the front, it slips into the outer barrel and centralises and supports the inner. It also provides a surface for the spring to bear against, without it the spring would get wedged in the gap. Link to post Share on other sites
fathom1001 Posted January 25, 2010 Author Report Share Posted January 25, 2010 If I remember correctly it was somewhere just about 400 fps or so originally. I'm going home next weekend so I'll take another look at the hop then. And I always thought that tiny pocket in your jeans was for loose change, although I barely ever use it for anything Link to post Share on other sites
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