Lessons Learned AR9 building and a happy ending

PSA Products AR-9
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I hope this post helps out someone, and saves them time, effort, and abuse in forums from trying to get help figuring things out. My AR9 build was a nightmare and expensive, but I finally got a fully and reliably functioning AR9. I hope to summarize this in this post for future reference

I bought a PSA complete 10" upper I put on my Spike’s tactical STG9 lower.

When I first put the firearm together, the upper and lower marriage mated up extremely well and the bolt locked back. Took it to the range to sight and initial it worked perfectly. I used both OEM Glock 19 mags and PMAGs 15,21 and 27.

I use it in our unsanctioned NRA ARC rifle match. Was getting constant FTF, Stovepipes, and the last round never fed it just smashed into the chamber lip.

When the brace ban came around, I bought a guaranteed to feed 16" barrel, after installing still had FTF problems and the accuracy of the barrels was abysmal with 10"+ groups at 50 and 24" groups at 100. The 10" barrel was dead on and group around 2-3" at 100y prior to switching.

To cut to chase my fixes through money, time and frustration were:

The A2 bird cage worked fine on the 10" barrel, but was throwing the shots off on the 16" barrel. Solution was remove the A2 bird cage and replace it with a thread protector. Under 3" at 50 yards with some cloverleafing.

The fail to feed was corrected by bending the LRBHO wire on the lower up to take tension off the follower. This fixed the last round not feeding and smashing into the chamber lip. Once I bent the LRBHO wire up and let the proper tension on the follower to keep it from pushing the angle of the last round in the mag down, I got reliable feeding and LRBHO working. As for the guarantee to feed barrel it was refunded and the steeper cone on the chamber is not necessary to feed. Both Glock and PMAGs work fine.

As a sidebar, an ARC peer I shoot with just got a Sig MPX 16". It does not have a muzzle device on it. He said he spoke to a Sig Armorer and they recommend to not put any muzzle device on the barrel. On yet another note, he claims that if he does not keep the bolt heavily lubed it will stove pipe.

I hope this save someone some time and effort as I saw many others in other outside forums with similar problems but no one offer any solutions other than abuse.

However from previous posts in these forums, it was suggested to remove the A2 bird cage which I was not able to do immediately. I had to buy a receiver vise block, breaker bar to get the birdcage off. Whence I did so, Voila accuracy came back. I was a bit skeptical because it made no issue on the 10" barrel just on the 16".

Thanks for everyone’s help and guidance. Problems solved. Wish you luck with your builds. I am working on a 6.5 Grendel at the present, for F Class matches.

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Your observations and solutions to the FTF problem may be very helpful to other firearms enthusiasts, especially those facing similar problems.
Your efforts in replacing the A2 birdcage with a thread protector and LRBHO wire bending have yielded positive results and have helped improve the reliability and accuracy of your AR9. This is a great example of how, with intelligence and patience, you can solve gun problems and achieve the desired results.

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similar story, i put random parts together that fit, sorta like the circle square triangle thing they used to have us solve in school except i learned how to hack that by putting the ball in the square hole… luckily carbines are no different and my 9mm pcc was born…

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Sorry you had these issues but you pressed on! Like many other’s on this forum we like to build our own. 3-4 yrs ago l got the itch for a 9mm pcc but l chose to buy not build due to it can/will be picky. I went with Foxtrot Mike pistol and a FM lower with a 16" DTT upper. Wasn’t long ago l removed the birdcage too on the 16". And recently bought a Diamondback pistol all 3 has the LRBHO. Not one hiccup except now the LRBHO is not working all the time. The mags are as follows: Pmags, Promag and cheap ETS…15,21 and 33 rnds. I believe the springs are now too weak to engage. Many operators here swear by Glock OEM mags…now l know why! Good intel on your part and thanks for posting!
Question: l wonder if l can purchase Glock spring/follower kits and will it fit these aftermarket mags?

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“Question: l wonder if l can purchase Glock spring/follower kits and will it fit these aftermarket mags?”

I called the Glock Store as I thought a heavier spring would solve the problem. The answer I got from the lady who I spoke with said no, the spring are not heavier and would not solve the problem. As for them fitting aftermarket, I cannot answer that. I would call the Glock Store and speak to them as to if they would fit aftermarket mags. My PMAGs work fine now in my AR9. I use the 15,21 and 27 rd. I only have 15 rd Glock OEM mags from my G19 carry and I prefer not to use them other than my carry mags. In ARC you can drop the mags on non mag retention stages so I use the cheaper PMAGs for ARC matches which are not sanctioned and not shooting for money or cars. So I use the cheaper mags for abuse use.

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Thank you for contacting them! And your reply

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All in all, for what it is worth, buy a factory if you want accuracy and reliability. I would have gotten a CZ Scorpion or Sig MPX or Beretta CX4 Storm or S&W Response or Colt M4 PCC Carbine if they were available at the time. I jumped into this AR9 endeavor when my only available option in beginning of 2022 was a Spike’s Tactical ST9G lower sitting in the case at Sportsman Warehouse. So i got the Build Fever for my PCC and bought it. While it works now, I really wished I bought factory for what I wanted it for. My other advise is an AR was designed for 5.56/.223 when you build an AR in .223 it is a complicated but when you build in a caliber other than 5.56/.223 it is a crap shoot. My opinion and please don’t take it to heart. PSA forum rocks, I posted in other forums and got abused. Everyone is courteous, consider, and complimentary in this forum and I appreciate the help, support and good words. Thank you.

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I also recently bought nearly this exact same setup.

Would you be willing to post a couple pictures of how you bent the bar?

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Welcome to the PSA forum! Which setup you asking about?

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Welcome to the PSA community forums :us:@samuelhastings

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Maybe not looking at this forum correctly but I was wondering about ajn1963s a9 that he had to bend.

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Are there any tricks to suppressing a Foxtrot mike or other similar 9mm carbine?

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Main thing is checking suppressor alignment. You may need to change out the buffer or recoil spring depending on what ammo you shoot

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Thank you, this is a good read. Im having acciracy inconsistency with a new factory PX9 with 8in. Im having 6in grouping at 15yds while my other builds consistently put rounds on top of each other. I will trythe birdcage removal and another optic.