AR-9 Stovepipe problem

[22BR]

A 16” 9mm upper on a 80% build lower with a standard AR-15 parts kit. Feeding and firing work great - however, nearly every ejected round ‘stovepipes’ badly. Ammunition is 135 gr. RN / slightly supersonic but haven’t chronographed from this barrel.

A). Do I need to change the buffer/spring? Suggested specs?

B). Reliable vendor for the above?

Thank you.

 

[NIGHTLORD40K]

Have you checked the ejector for any damage and confirmed its screws are tight?

 

[22BR]

Ejector is tight - no damage. My line of thought is - bolt is not moving far enough back and catching empty case as it moves forward (case doesn’t have time to clear bolt as it closes). It is a PSA upper / parts kit is generic AR-15 rifle parts.

 

[NIGHTLORD40K]

I got my PSA9 as a complete rifle, Ill see if I can weigh the buffer that came with it. Mine runs like a tungsten top.

 

[NIGHTLORD40K]

My buffer is 5.5oz, 3.25in long, standard M4 carbine tube. The bolt is a PSA Gen 4.

 

[22BR]

I will check mine - thank you.

 

[marvin02]

Great web site with AR9 info:

https://blowback9.wordpress.com/blog/

 

[12Bravo20]

5.5 ounces is the minimum buffer weight for blow back 9mm AR's. Most will run either a 7.5 or 8.5 ounce buffer. Some will run even heavier buffers. My CMMG Colt style runs fine with a 5.5 ounce bolt.

@22BR is your rifle Glock style or Colt style? If your is a Colt style, then check to make sure the ejector is signed up correctly. You want the Colt style ejector to be close to the center line of the bolt.

I recommend using an extended 9mm buffer or a spacer with a standard carbine buffer. This keeps the bolt from going to far back and then slamming into the bolt catch and breaking it.

 

[22BR]

Well - looks like a 2 oz. / 3” buffer is totally inappropriate for this application! Thanks for the input - working on getting this fixed ASAP

It is a ‘Glock’ setup - only glitch so far / should be fully functional soon.

 

[Uffdaphil]

My PSA Glock AR9 had stovepipes and intermittent full auto with the light buffer. An 8.5 oz heavy buffer solved both issues. Fun affordable gun, but the gas clouds with a suppressor were intolerable. My Scorpion
Evo pistol is worth the extra $$$ to me to escape the gas to the face.

 

[22BR]

The 8.5 oz. buffer is on the way. Eventual plan is to suppress it - will have to see if there is a way to make the gas amount acceptable. Thanks for the input.

 

[22BR]

New 8 oz. buffer - all is well. Feeds, fires, ejects reliably with no issues. Thanks for the suggestions.

 

[12Bravo20]

Glad to hear that a proper weighted buffer fixed everything for you.

 

[NIGHTLORD40K]

New 8 oz. buffer - all is well. Feeds, fires, ejects reliably with no issues. Thanks for the suggestions.