New AR Issues

[jthoma24]

All,
I just completed my latest build. I took it to ACG on Saturday and was having some FTF/FTE, and the bolt not locking back on the last shot. It is obviously short stroking. Any advice on what it might be or what to look for?

Upper - Stag Arms 3 g 18in
Lower - PSA - w/ geissele dynamic trigger installed
Buffer tube - spikes
Buffer and spring - brownells
BCG - Stag

 

[Jasonshooter]

Sounds like your gas block isn't properly aligned , not allowing the bolt to be pushed all the way back . Most likely a gas issue ..

 

[clandestine]

Do you have spare bolts, lowers, and buffers to troubeshoot it with?

If the ammo is steel cased, pmc brass, or that remanufacured junk then the ammo may be the problem.

Have different mags to try?

 

[jthoma24]

Yes I have other buffers/Spring/bolts to try. I am hoping it is not a gas issue since the upper came complete from stag. I was also thinking it might be hammer drag. Do you know how to test for that?

Do you have spare bolts, lowers, and buffers to troubeshoot it with?

If the ammo is steel cased, pmc brass, or that remanufacured junk then the ammo may be the problem.

Have different mags to try?

 

[F-Stop]

What ammunition?

 

[clandestine]

Yes I have other buffers/Spring/bolts to try. I am hoping it is not a gas issue since the upper came complete from stag. I was also thinking it might be hammer drag. Do you know how to test for that?

If its a geisele trigger its not hammer drag.

It could have a mis alligned gas block/fsb or an undersized gas port. The gas port should be the last thing to address.

 

[jimbobborg]

Are you running it with enough lube? I've seen people with new ARs with two drops of oil in there. Just sayin'.

 

[ObsceneJesster]

Is that a mid-length or a rifle length gas?

What Buffer Weight are you running?

What ammo are you shooting?

 

[Boom Boom]

Is that a mid-length or a rifle length gas?

What Buffer Weight are you running?

3G is rifle-length gas system. I'm thinking the buffer and/or spring might be too heavy.

 

[jrumann59]

Could be ammo, one f my ARs hates PMC bronze but will fire any other brand to date without issue. IIRC PMC Bronze is a little weak.

 

[clandestine]

Could be ammo, one f my ARs hates PMC bronze but will fire any other brand to date without issue. IIRC PMC Bronze is a little weak.

Agreed. Its also quite inconsistent from round to round.

 

[jthoma24]

I was feeding it cheap steel case ammo. next time I take it out I will bring another BCG, Buffer & spring and different ammo. and start eliminating the possibilities.

 

[clandestine]

Use some brass cased ammo. Don't use PMC, reloads, remanufactured, or steel cased ammo to work out the bugs.

 

[ObsceneJesster]

18" Rifle Length Gas as you know is a very soft shooter. Some just don't like cheap steel case ammo or other low powered stuff.

If you don't already have a carbine buffer in there, I would put one in. This would probably give you the best results when running low powered ammo.

This is one of the reasons why they started the "intermediate" gas length. It makes the 18" barreled AR's a more reliable over a wide range of ammo. If I was shooting nothing but 5.56 and good quality ammo, I'd rather have the Rifle length but if I wanted reliability with the cheap stuff, I'd probably go Intermediate or Mid-Length. That's not to say a 18" Rifle Gas can't be reliable with cheap ammo because many of them are. It just takes a little bit more tuning to get it there.

If you eliminate all the small stuff and you determine everything is installed correctly, it could just be the gas port is on the smaller end of the spectrum. You could look into having someone open it up a little bit if you want to shoot the cheap stuff with reliability.

 

[Jradack]

Like mentioned before, prolly a gas issue. I fought similar issues with my 20" hbar build. I had Cheapo gas block and couldn't get it to align. I fixed the issue with a Yankee hill gas block.

 

[armed ferret]

Like mentioned before, prolly a gas issue. I fought similar issues with my 20" hbar build. I had Cheapo gas block and couldn't get it to align. I fixed the issue with a Yankee hill gas block.

OP's upper is a complete upper from a very reputable manufacturer, not a build with random parts. Given his circumstances, underpowered ammo is most likely the culprit.

 

[SCARCQB]

Are you running it with enough lube? I've seen people with new ARs with two drops of oil in there. Just sayin'.

+1

Lubricate the the crap out of it. Critical for breaking in a new AR.

 

[amoebicmagician]

If it's a rifle length gas system, especially with anything under 20 inches, I'm inclined to believe it's the buffer or spring. The farther up you put the gas port, the less time the bullet is in the barrel providing pressure after it passes the port and starts the reloading process, the opposite of the problem usually seen with carbine length gas systems in 16 inch barrels, which is tending to be a little violent in the rearward stroke due to the bullet being in the barrel a comparatively long time after passing the port, and also the gas having to travel a much shorter distance down the tube to reach the breech resulting in higher pressures.

I'd address the problems in this order:

Lube the shit out of it, try it out
If not working, swap out the buffer
If still not working, swap out the spring
If STILL not working, address the gas port/front sight alignment or sizing issues.

You could also bring a variety of ammo, but I personally would want my gun to run with whatever I feed it, and so far I haven't found this to be an unattainable goal, with enough troubleshooting I haven't owned an AR yet that hasn't eventually turned out at least cycling reliably

 

[ObsceneJesster]

Is there a echo in this thread? :-)

Sent with a Gen 2 Nexus 7

 

[303_enfield]

I was feeding it cheap steel case ammo. next time I take it out I will bring another BCG, Buffer & spring and different ammo. and start eliminating the possibilities.

Part in RED. DON'T CHANGE ANYTHING OUT BUT THE AMMO! Get some USGI M193 ammunition for break in. Don't ever try to break in an AR with cheap, under powered, cheap, POS ammo. Your upper was test fired before it was shipped. Now, not all manufactures do that but Stag does.