Friends AR problem

[BDA.45]

So my buddy finished a build recently and shot it (kinda) the other day. He's having problems and we can't figure it out and need help.

Seems to me he's getting light strikes and when it does shoot it short strokes. Hes determined the problem is in the upper. At first we thought it was the hammer spring but swapped and it shot fine. The only things I can think of is a misaligned gas block or something in the BCG. Gas rings.....What am I gonna look for in a block alignment issue? I'll try to get more info out here as it comes in. We're in text tag mode right now....

L one is from the build....

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[MilitantBEEMER]

Had a similar problem with a friends recent build and it was s weak buffer spring not pushing the bolt all the way forward. Switched out with a new spring and it was rock n roll

 

[BDA.45]

Had a similar problem with a friends recent build and it was s weak buffer spring not pushing the bolt all the way forward. Switched out with a new spring and it was rock n roll

He's swapped the upper out thinking about the FCG and everything ran fine.

 

[MilitantBEEMER]

He's swapped the upper out thinking about the FCG and everything ran fine.

It may be under gassed? Not sure? I would still try the buffer spring and maybe a lighter BCG and see if either of those make a difference. Good luck!!

 

[BDA.45]

It may be under gassed? Not sure? I would still try the buffer spring and maybe a lighter BCG and see if either of those make a difference. Good luck!!

Thanks man. I also made the suggestion of swapping parts. Dudes built like 10-15 ARs and this is the first time he's ran into an issue.

 

[drstrangelove]

Stronger hammer spring.
Polish the firing pin shaft and make sure no burs in BCG firing pin channel.
Make sure barrel is correctly headspaced... too deep will allow the case to move away from the BCG when the pin strikes.

 

[BDA.45]

Stronger hammer spring.
Polish the firing pin shaft and make sure no burs in BCG firing pin channel.
Make sure barrel is correctly headspaced... too deep will allow the case to move away from the BCG when the pin strikes.

Is there a way for him to test head space without a gauge? He said he's never spaced any builds, just torques them to spec....

 

[Certaindeaf]

Is there a way for him to test head space without a gauge?.

Yes there is, if he's getting light strikes and when it does shoot it short strokes the headspace is off.




















JK, I have no idea.

 

[BDA.45]

Yes there is, if he's getting light strikes and when it does shoot it short strokes the headspace is off.




















JK, I have no idea.

LOL, fukr....

 

[drstrangelove]

Is there a way for him to test head space without a gauge? He said he's never spaced any builds, just torques them to spec....

Headspace gauges are cheaper than a kaboom. $30

 

[BDA.45]

Headspace gauges are cheaper than a kaboom. $30

Very true. You know of anyone locally that sells em? I'd start makin calls right now but everyone's most likely closed

 

[eldbillbo]

Check his gas tube alignment make sure it's not binding inside the gas key the bolt should close and lock up with very little resistance.

Some guys don't get the gas port lined up with the barrel nut correctly and the gas tube goes off the side a little just enough to cause resistance in the key.

 

[HB of CJ]

Private contact me via this forum if you want to. We will get you going. Could be a combination of several little or big things, parts or build procedures. Respectfully.

Hundreds of AR15 Builds.

Edit: Private Contact Established.

 

[BDA.45]

Check his gas tube alignment make sure it's not binding inside the gas key the bolt should close and lock up with very little resistance.

Some guys don't get the gas port lined up with the barrel nut correctly and the gas tube goes off the side a little just enough to cause resistance in the key.

Thanks. He's actually gonna give me the upper sometime this weekend. I'll try everything everyone has responded with. I'll also try to rule out anything that has to do with the lower.

 

[DirectDrive]

So my buddy finished a build recently and shot it (kinda) the other day. He's having problems and we can't figure it out and need help.

Seems to me he's getting light strikes and when it does shoot it short strokes. Hes determined the problem is in the upper. At first we thought it was the hammer spring but swapped and it shot fine. The only things I can think of is a misaligned gas block or something in the BCG. Gas rings.....What am I gonna look for in a block alignment issue? I'll try to get more info out here as it comes in. We're in text tag mode right now....

L one is from the build....

View attachment 361303

Gas block alignment - (sounds like Suspect #1 here)
After being shot a few times there will be a carbon trace around the gas port on the barrel.
This is visible with the gas block removed.
A nice, concentric circle around the barrel's gas port is what you want to see.
(the gas block port has a larger opening....think funnel)

Verifying gas tube/gas key alignment is always good idea and something an experienced will do during the build.

If a carbine buttstock system (telestock) use a Standard Weight (carbine) buffer and a standard weight (carbine) spring for break-in.
Use full power XM193 or M855 ammo for break-in.
Play with different buffers/springs AFTER the new build is running if so desired.
Play with weaker ammo AFTER new build is running if so desired.

Might have to send for the headspace gauge(s) or find a Black Rifle Competent gunsmith to check headspace.
If you are only going to have one, then the M16 Field Gauge is the one to have. (there are other lengths)
BROWNELLS 5.56MM MAXIMUM HEADSPACE GAUGE | Brownells
The bolt should not go into battery with this gauge in the chamber.
Follow the detailed instructions and never let a BCG slam into the gauge.

 

[edslhead]

Gas block alignment - (sounds like Suspect #1 here)
After being shot a few times there will be a carbon trace around the gas port on the barrel.
This is visible with the gas block removed.
A nice, concentric circle around the barrel's gas port is what you want to see.
(the gas block port has a larger opening....think funnel)

Verifying gas tube/gas key alignment is always good idea and something an experienced will do during the build.

If a carbine buttstock system (telestock) use a Standard Weight (carbine) buffer and a standard weight (carbine) spring for break-in.
Use full power XM193 or M855 ammo for break-in.
Play with different buffers/springs AFTER the new build is running if so desired.
Play with weaker ammo AFTER new build is running if so desired.

Might have to send for the headspace gauge(s) or find a Black Rifle Competent gunsmith to check headspace.
If you are only going to have one, then the M16 Field Gauge is the one to have. (there are other lengths)
BROWNELLS 5.56MM MAXIMUM HEADSPACE GAUGE | Brownells
The bolt should not go into battery with this gauge in the chamber.
Follow the detailed instructions and never let a BCG slam into the gauge.

Your hyphaduphalator is way off I got the specs. Hit me up

 

[v0lcom13sn0w]

headspace

 

[DirectDrive]

Your hyphaduphalator is way off I got the specs. Hit me up

Tryin' out a new chip.
Gets the space/time continuum a little wonky.

 

[ORYGUNHolsterCompany]

So my buddy finished a build recently and shot it (kinda) the other day. He's having problems and we can't figure it out and need help.

Seems to me he's getting light strikes and when it does shoot it short strokes. Hes determined the problem is in the upper. At first we thought it was the hammer spring but swapped and it shot fine. The only things I can think of is a misaligned gas block or something in the BCG. Gas rings.....What am I gonna look for in a block alignment issue? I'll try to get more info out here as it comes in. We're in text tag mode right now....

L one is from the build....

View attachment 361303

As for your light strike issue, I usually check firing pin lengths and look for wear around the tip of the pin. I have seen a bunch of firing pins that are too short or the diameter becomes too large and won't clear the bolt. Have also seen forgotten shortened pins from gun shows show up in the customers rifles.

As for short stroking, the gas issue seems to be a consensus at this point.

Good luck, if your out near Hillsboro I have a go/no go gauge to test the head spacing. Pm me if I can help.

 

[titsonritz]

The only things I can think of is a misaligned gas block or something in the BCG. Gas rings.....What am I gonna look for in a block alignment issue?

It shouldn't be gas rings unless this a used bolt and/or rings or crap manufactuer. Simple test...take the assembled BCG, pull on the bolt to put it the forward position, place the BCG on the hard flat surface on the bolt face, if the carrier drops under its own weight the rings are bad, replace them.

Pics would be helpful when discussing gas block alignment, as would more info. Is the barrel dimpled for a the set screw? If not it can and most likely will eventually cause gas problems. If the gas tube is slightly misaligned it can push the gas block forward on the barrel cutting off gas (see below for testing this). What is the barrel profile? Does it have a gas block/FSB journal and is the gas block pushed tight against it? It should not be, the location of the gas port to the journal shoulder will leave a gap for the handguard retainer cap.

Check his gas tube alignment make sure it's not binding inside the gas key the bolt should close and lock up with very little resistance.

Some guys don't get the gas port lined up with the barrel nut correctly and the gas tube goes off the side a little just enough to cause resistance in the key.

To properly test the gas tube/carrier key alignment, disassemble the BCG, install the field stripped carrier in the upper w/o the charging handle and operate by hand, there should be no resistance.

headspace

Good luck, if your out near Hillsboro I have a go/no go gauge to test the head spacing.

Headspace is NOT an issue to typical AR building. If you are manufacturing barrels and installing barrel extensions that is a different story. Out of spec chambers is the most likely culprit when people refer to headspace on ARs. It is pretty common for lower tier barrels to lack true 5.56x45 chambering despite what is stamped on the barrel. The only gauge needed for the AR owner is the field gauge DirectDrive linked above (though a GI issue one is better due the ejector cut, but good luck finding one) and that is to tell if the weapon has been shot-out not headspaced correctly, again that is the job of the barrel manufacturer.