5.56 Gas Problem

[Bocephus1776]

Greetings all,

I recently built triplets 5.56 AR-15's. All 3 have a Ballistic Advantage Modern series Government profile mid-length barrel (.750), Aero low pro gas block, Aero gas tube, Fail Zero nickel boron M-16 BCG, KVP carbine tube with spring and 4.3 oz buffer.

2 of them run great. Zero failure to feed, fire, or ejects, brass around the 4 o'clock position around 7 ft.

1 of them seems under gassed and short stroking. Ejects around 4 o'clock bout only a couple feet away and the bolt never locks back after last round. If I use my old MFT 30 rd mags it feeds and fires without issue but if I use a new 10 rd PMag it has intermittent failure to feed. The bolt slams the new round into the feed ramps.

Mostly using Federal black box .223 in 55gr FMJ

I've emailed BA to see what the gas port size is supposed to be but figured I'd ask y'alls opinion while I wait. Thanks for the help.

 

[aslrookie]

My opinion, stop buying cheap barrels.

 

[Powder_Burns]

Double check gas port/block alignment.

 

[_Windrider_]

Greetings all,

I recently built triplets 5.56 AR-15's. All 3 have a Ballistic Advantage Modern series Government profile mid-length barrel (.750), Aero low pro gas block, Aero gas tube, Fail Zero nickel boron M-16 BCG, KVP carbine tube with spring and 4.3 oz buffer.

2 of them run great. Zero failure to feed, fire, or ejects, brass around the 4 o'clock position around 7 ft.

1 of them seems under gassed and short stroking. Ejects around 4 o'clock bout only a couple feet away and the bolt never locks back after last round. If I use my old MFT 30 rd mags it feeds and fires without issue but if I use a new 10 rd PMag it has intermittent failure to feed. The bolt slams the new round into the feed ramps.

Mostly using Federal black box .223 in 55gr FMJ

I've emailed BA to see what the gas port size is supposed to be but figured I'd ask y'alls opinion while I wait. Thanks for the help.

Did you build them yourself? Maybe the gas port isn’t perfectly aligned on the gas block.

is it every pmag or only a certain one? I’d take careful notes and start swapping parts with a functional one and see if you can isolate the failure.

 

[Bocephus1776]

Did you build them yourself? Maybe the gas port isn’t perfectly aligned on the gas block.

is it every pmag or only a certain one? I’d take careful notes and start swapping parts with a functional one and see if you can isolate the failure.

I only have that 1 PMag. I can get a different one though. I did swap out the buffer and spring with one that works and they do the same thing. Gas block looks like it's lined up but I haven't had time to take it apart yet. I'm going to try that this weekend.

 

[Bocephus1776]

My opinion, stop buying cheap barrels.

What barrels do you recommend? I'm not shooting competitions. All my other BA barrels work great and shoot sub moa at 100 yds.

 

[Texasflyer]

Check your gas ring alignment on the bolt. If the rings arent staggered this can happen.

 

[_Windrider_]

What barrels do you recommend? I'm not shooting competitions. All my other BA barrels work great and shoot sub moa at 100 yds.

Nothing wrong with BA barrels for blasters.

 

[Neurotic]

Another easy test: swap BCGs...

I had a similar issue and it was the BCG. I didn't further isolate the issue, but it could've been an excessive clearance issue at any of the bores (gas key, bolt tail or main bore).

 

[Neurotic]

Just re-read the post. Does the pmag sit higher in the short stroking lower compared to the others?

 

[aslrookie]

What barrels do you recommend? I'm not shooting competitions. All my other BA barrels work great and shoot sub moa at 100 yds.

What does competition have to do with it if the rifle isn't functioning properly? Quality barrels means consistent performance. When you buy cheaper barrels, you get more variance and less consistency. Criterion, white oak armament, and compass lake engineering are just some of the barrels that have good results. The barrel is the heart of your system. I'd rather have a nice barrel with cheap receivers than top notch receivers and cheapest barrels.

You can play with various things if you want, or just send BA the barrel back and have them send you a new one (if they still do that).

 

[Bocephus1776]

What does competition have to do with it if the rifle isn't functioning properly? Quality barrels means consistent performance. When you buy cheaper barrels, you get more variance and less consistency. Criterion, white oak armament, and compass lake engineering are just some of the barrels that have good results. The barrel is the heart of your system. I'd rather have a nice barrel with cheap receivers than top notch receivers and cheapest barrels.

You can play with various things if you want, or just send BA the barrel back and have them send you a new one (if they still do that).

I was just saying that I don't need a Proof Research in these ones. I have different guns for different uses. These are just fun plinking firearms. Haven't had an issue with my 8 other BA barrels. I'll look into the ones that you suggested though. Thanks for the help.

 

[Bocephus1776]

Just re-read the post. Does the pmag sit higher in the short stroking lower compared to the others?

I'll have to check that tonight. Didn't think about that. The springs are definitely stronger in the pmag. The other ones have a couple thousand rounds through them and are a few years old. The pmag is brand new. I'll swap out the bcg's next time I'm able to shoot and see if that does anything.

 

[Bocephus1776]

Thanks for the help fella's. BA got back to me and said the port is supposed to be .0785" so I'll check that tonight. They also recommended a standard buffer but I run a H2 in all my other ones with zero issue.

 

[permaximum78]

One more thing to check would be the gas key on your bolt carrier. I've seen high end carriers be lose out of the box and spent hours chasing problems.