Compression Problem

[delta76]

Just opened up an Aftermath Broxa to start re-shimming and upgrading and I noticed that there is no compression at all when pushing the piston into the cylinder with the nozzle covered which seems very odd as just before taking the gun apart it was shooting regularly, any suggestions?

[m102404]

None? Nothing? Not even a hiss?

Then your o-ring isn't expanding and sealing as you push it forward.

1. Give it a sharp, quick push (like your mainspring would)
2. Make sure it's not all gunked up with really heavy grease.

[delta76]

Very little even with a quick burst, no sensation of pressure on the piston at all, Aftermath has a tendency off loading mechboxes with loads of think green grease and some has gotten on the o-ring and piston head could that be the problem? What I don't understand is how it was shooting at all before disassembly.

[Styrak]

Take off the o-ring and stretch it out. Put it back on and test again.

[delta76]

Stretching it did the trick thanks

[m102404]

Stretching it is temporary. It's just rubber and will collapse back to it's "too-small" size.

Either replace the o-ring with another one that is sized correctly or change the dimensions of the existing o-ring.

If you stretch the oring over the outside of the cylinder (might be snug if it's too small to being with), evenly heat it with a lighter and let it cool completely...it will soften and reharden into the larger diameter.

Degrease it first (just a good wipe with a towel/tissue is fine). Regrease it afterwards.

[{CAF} Bubbles]

i had the same issue with my broxa, only mine was miss firing. i took it to my local gun tech. and replaced the o ring. that seemed to do the trick... but mine is still on and off with its shooting consistency... they say the hi-cap mag has about a 10% miss fire anyway... which i would agree with. as for the grease. when i opened mine up there wasnt any at all... i wound up having to put some in. from what i understand these aftermath guns need alittle tlc and preventative mant. when you first get them.... ohhhh and keep it clean. these things jam every once and awhile..... or at least mine does... lol. it goes along way towards inspiring confidence... in your ability to back track and find a safe place to unjam it... lol

anyhow... i havent been to disappointed in the gun. for what i paid for its pretty good and a great starter gun to cut your teeth on.... from what i understand its compatible and up gradable with other mp5 models...

cheers

[delta76]

Purchased mine a while ago and put about 15000 rounds through it stock until I started getting some whine from the motor, adjustments only temporarily eliminated the loud whining so I decided I'd take it apart regrease, reshim, put in some metal bushings and see what happens, really looking forward to seeing how far I can go with this and there's a lot to improve the stock compression parts are not even up to par for a low end and I'd like to throw in a tight-bore and a new motor, a nice paint job would be nice and maybe even a replacing the upper receiver with a metal one but that might be wishful thinking...

[{CAF} Bubbles]

i just fielded mine tonight after getting it out of the shop. its still miss fires abit, but not as bad as before. i got some new mags... mag mags. the bb's i used when i was gameing where the facilities bb's and it didnt seem to skip too much. however the bb's i have at home which are .20's seem to make my gun miss fire alot more???? i agree these guns do need a h#ll of alot of work... but still... its smthng to me busy. i have a feeling though the bb's may have smthng to do with it a bit???? any thoughts

[ujiro]

Its true. High quality BBs will get you much better consistency. Fewer misfires.