Piston Rifles

[Polar Bear]

A buddy of mine is having problems with his. Stag Arms full auto. No mater if it is in FA or semi you can not make it through a mag without a failure to fire. Tried diff mags and ammo. Have used the mags and same ammo in other AR's no problem. Any guesses on what the problem would be?

 

[Raksasa Kotor]

Firing pin needs to be sharpened.

 

[Raksasa Kotor]

But seriously, without knowing the actual malfunction (fail to feed, eject, etc), I would suspect either insufficient gas pressure hitting the piston and causing the weapon to not fully cycle, or too much gas pressure throwing off the timing of the firing cycle enough to cause a malfunction.

 

[x SF med]

agree with Rakasa Kotor, check your bleed setting on the rifle and see if it can be set more to the piston.

and this is why I love my FN, no issues with the gas circulation to the piston, if it ever does I know how to reset the bleed.

 

[amlove21]

But seriously, without knowing the actual malfunction (fail to feed, eject, etc), I would suspect either insufficient gas pressure hitting the piston and causing the weapon to not fully cycle, or too much gas pressure throwing off the timing of the firing cycle enough to cause a malfunction.

3rd. only timy my HK 417 would malfuntion was when the gas key wasn't right.

 

[policemedic]

My LWRC is the same way. It's got a selector for suppressed/unsuppressed. If the STAG is the same, that may be the issue.

What specific malfunction is occurring?

 

[Slider496]

Wish I could help but Ive never had this problem. I had a stag model 2 and my dad had a model 8 and weve never had this issue. Best of luck to ya!

 

[parallel]

Failure to fire? Meaning the spent round ejects properly, the new round feeds properly, but doesn't fire? That sounds more like a "hard primer" issue with the ammo which might be exacerbated by a weak firing pin or a fouled firing pin (in need of cleaning).

If we're talking failure to eject I would suspect the gas pressure to be too high, which would not give the brass time to contract from being pressed against the chamber walls from the pressure before the ejector begins to act on it. If we're talking failure to feed I'd be looking closely at magazines first and the feed ramp and chamber specs next.

 

[Diamondback 2/2]

Everyone has pretty well covered my basic thoughts. I will say if it is a "failure to fire" meaning round chambered, hammer droped, round didn't go off. You might also look at the trigger group hammer spring. Especially if the full auto has been used a lot, and even more so if your buddy put a reduced spring kit in it. But outside of that, if its a feeding problem, 9 out of 10 times its a gas port/key issue on the piston guns.