Is it the magazine or gun thats broke?

[Goge]

The gun is a TM Steyr Aug, the Mags are KingArms 45rnd Low-Caps

I just finished putting in a guarder infinite torque tune-up kit kit in my AUG and everything is smoooooth. It sounds crisp, no grinding, shimmed perfectly, switched to Deans Ultra connectors. Fixed the semi-fire problem I had and everything seems to be perfect EXCEPT...
Only 1 out of 4 full auto shots actually fire a BB and semi is 1 in 10.
BUT
If I tilt the gun 180 degrees and fire it 'upside-down' with the mag gravity feeding it shoots 100% of the time on semi and full auto.

All my mags were full of BBs and they were left there from my last game sometime in the summer. August I think.

Am I doomed?

SOLUTION:
The mag was sitting loose on the hop-up feed, pushing up on the mag would allow the bbs to feed correctly.
I noticed the way the mag works is the actual mechanism slides out the top of the plastic shell and is held in place by a small screw at the bottom that runs through a slide on cap/cover. I shimmed/stuffed the bottom with cotton balls (hey it was close and actually works really well) so that the nozzle of the mag is now 3 mm higher then it was compared to before and now its shooting at 100%.

Thanks everyone for your help.

[AngelusNex]

mag springs may all be foobared.

[theguy]

Your mags were filled with BBs since August?

That would do it...

What brand are the mags?

and what model/brand is your gun?

[coach]

if you fill the mag again and pull the little release tab, do the BB's come flying out?

open the mag and stretch the spring a bit or try a new mag.

[Goge]

@theguy: TM Steyr Aug, KingArms 45Round Lo-Caps

@coachster: When I fill the mag and hit the release they do shoot out.

What could make a mechbox function differently when upside-down?

[theguy]

Originally Posted by Goge

What could make a mechbox function differently when upside-down?

Nothing really.

All that turning the gun upside down does, is allows it to feed even though the spring in the mag isn't doing its job.

Gravity pushes the BBs into the hop-up chamber, so the spring in the mag doesn't have to.

[coach]

your tappet or tappet spring could be broken.

when you dry fire, can you clearly see the nozzle move fully forward and back?

[theguy]

Originally Posted by coachster

your tappet or tappet spring could be broken.

when you dry fire, can you clearly see the nozzle move fully forward and back?

But the fact that it still feeds when the gun is upside down leads me to believe that the tappet is functioning fine.

[Goge]

Yea I forgot to mention it in my previous posts.

With a light down the feed tube I can see the nozzle moving forward and back smoothly.
Should it be resting forward or back? what I mean is with the spring decompressed after a full cycle should I be able to see the nozzle?

Where the nozzle stops is pretty inconsistent.

[coach]

Originally Posted by theguy

But the fact that it still feeds when the gun is upside down leads me to believe that the tappet is functioning fine.

true but it's still possible. stranger things have happened inside a mechbox. I'm sure everyone who has worked on a mechbox has encountered a gremlin or 20!

goge, go get a friends mag or try stretching the spring before cracking the mechbox open again.

is the nozzle stopping inconsistent on semi or auto?

[Goge]

@coachster: on semi. the nozzle was moving correctly when I ran it before placing it back in the gun.

how can I stretch it. I think I read somewhere boiling works, anyone tried that?

[coach]

Originally Posted by Goge

@coachster: on semi. the nozzle was moving correctly when I ran it before placing it back in the gun.

how can I stretch it. I think I read somewhere boiling works, anyone tried that?

open the mag up and physically remove the spring and stretch it with your hands! :banghead:

[Jugglez]

Does it work if you push the mag up into the magwell while firing?

Sounds like the mag is not mating properly with the hop-up

BB's flying out means the mag springs are working.
The mechbox sounds like it's fine too.

[Goge]

Thank you guys!
There is about a half centimetre of play and when I push up on the mag it fires 100% like when upside down. Not sure why I didn't try that before, I guess seeing the BBs in the mags and having just had the mechbox open had me worried.

Is there any known solution to a problem like this? Why wouldn't the mag be sitting correctly with the hop-up?

Thanks for the quick replies everyone!

[Jugglez]

Take a file and shave the bb retainer down about a mm.

The bb retainer is the trianglular piece at the top of the mag that holds the bb's from flying out.