A&K M249 fps low
 

I gotten a brand new A&K from RA... worked great out of the box. Swap spring out for a M100 spring shooting around 360 - 370fps for an outdoor game. Retested it a week later now the spring shoots around 270fps. So went and bought a Modify M110 spring into it and now it shoots at ~300fps.

Spring M100 has been changed. Rubber changed to Guarder clear. Was all done when it still shot around 360 - 370fps and gamed perfectly.

Since the fps drop after a week since the game, I thought the hop up was bad like all reviews said and ordered a CA hop up and installed it hoping it would an easy fix like others have done. Nope only help by about +10fps.

Can anyone give me a clue to as why the fps drop like crazy? So I can game with this massive puppy and create a shower of bbs.

How well is the hopup chamber mating with the gearbox?

Flip up the feed cover and see if it (and the outer barrel) are being pushed forward.

First thing, make sure your are "clicking in" the barrel assembly properly, it has to make distinct "click" sound..

One of my A&K is now a bitch to connect back in, doesnt click in, just sits tight.

Mating is tight up against each other. If you mean by pushed forwarded, there is no gap between the hop up unit and the mechbox.


I hear the "click" sound everytime I put it back in. Took me a couple of tries the first time I got it and figured it out. LOL!


I put the original M140 spring into it and now it shoots at 370fps. I'm definitely don't want to game with a M140 and tear the internals to shreds.

A 140 spring should deff bring the fps over 370 fps. With that spring 450 is about normal. I think you need someone to take a look at that. Are you certain that your spring guide it locked into the gun and not partially out.

I have the same issues with my 60. It is the mating of the gearbox and hop up. Even though it looks lIke it's tight, they're could be a leak.

No kidding with a 140 spring shouldn't that low at all. Spring guide is locked down and almost flushed with the rear of the gearbox.

Well I'm open to all solutions. Before sending to a gun doc and emptying my wallet.

there is a major air leak. And the air leak seems to get worse with the higher of a spring you are using.... Hop-up is a reasonable assumption, i would say it is mostly the bucking. Some air nozzles wont seal properly and like different angles. Look at the new and old bucking and compare them and see if the angles are different
But other places like the cylinder head, piston head (o-ring) and air- nozzle can get leaks after a short while too. Teflon tape around the cylinder head, and stretching out the o-ring on the piston head will help a lot