PSA 16” 300BLK issues

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jps1542
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PSA 16” 300BLK issues

Post by jps1542 » Wed May 22, 2019 6:43 pm

I recent picked up a 16” PSA 300 BLK upper. I am having some feed issues with supersonic ammo. Both with handlaods and factory. Ironically, subsonic ammo runs like a champ. Bolt locks back reliably on empty magazine with subs or supers. However I get 1-2 failure to feeds a magazine. The round will nose up into the chamber. On my 125 SST loads it is hitting the top of the chamber/lugs so hard it is bending or shearing off the plastic top. With factory FMJ, you can clearly see the bullet tipped scratched up. My first thought was it is overgassed. So I dropped in a geissele braided buffer spring and h1 buffer. Issue has persisted. I’m not new to the AR platform and have built two other 300 blackout rifles from ground up. But this is a first for me. I know magazines can be a factor so I have tried m2 and m3 pmags. Both 20 and 30 rounder. Same results. The 300blk specific mags seem to work flawlessly. Since this is a hunting gun, I would prefer to use a 20 or 10. If it is not a magazine issue, I am wondering if it is the feedramps. Any help would be appreciated.

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golfindia
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Re: PSA 16” 300BLK issues

Post by golfindia » Wed May 22, 2019 8:35 pm

Did you load the SSTs yourself? Feed one slowly while riding the bolt handle. Check to see whats happening when the cartridge comes free of the feed lips. I had to load some of those light plastic tip hornady bullets a smidge longer to keep them from launching up into the bolt lugs. If the round comes free from the feed lips and the tip isnt near the chamber, it gets hosed. Even if they feed, unchamber a round and check to see if the tip is mangled.

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dellet
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Re: PSA 16” 300BLK issues

Post by dellet » Thu May 23, 2019 9:38 am

If that is pistol gas like most PSA uppers, treat it Iike it’s over gassed, because it is.

The heavy spring combined with a light buffer cancels out any gain you might have had by installing it. Another clue would be that Giessele warns against using that spring with subsonic Blackout.

Normal buffer for pistol gas would be an H2. Some companies that put together 16” pistol gas rifles recommend an H3 for supers or have adjustable gas blocks. You might get by with the heavy spring and H2 combination.
300 Blackout, not just for sub-sonics.

jps1542
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Re: PSA 16” 300BLK issues

Post by jps1542 » Thu May 23, 2019 1:36 pm

These are loaded at 2.1 COAL. I could possibly do a tad longer, but I would be past the cannelure. I have noticed riding the bolt slow and watching it is the rounds to like to jump from the magazine. That being said, I have yet to recreate the malfunction hand cycling the gun. On the spring/buffer, I’m aware about geisseles warning in regards to it and sub Sonics. Yet I have not experienced any issues of any kind with subsonics. I have not tried a h2 or h3 Buffer yet because I don’t have any lying around. Almost all my other AR15s are rifle gas for 223(3 gun rifles). My other blackouts are all standard carbine springs and buffers. But they are also 7-11” barrels.

golfindia
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Re: PSA 16” 300BLK issues

Post by golfindia » Thu May 23, 2019 1:47 pm

I definitely had to load them longer than the cannelure..... according to my notes, 2.1 is right at the cusp of where my feeding issues appear.

jps1542
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Re: PSA 16” 300BLK issues

Post by jps1542 » Thu May 23, 2019 5:16 pm

What length did you end up at?

golfindia
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Re: PSA 16” 300BLK issues

Post by golfindia » Thu May 23, 2019 6:37 pm

125 SST 2.20

I started the 125 sst at 2.1. Maybe something shorter than 2.1 would feed better... I also use 18g powder for that one (2257fps/16"), so it's pretty full.

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Re: PSA 16” 300BLK issues

Post by AR-300 » Thu May 23, 2019 9:18 pm

Put a fresh o-ring in the BCG
That worked for me
PSA 10.5" & 16'' FN CHF CL 300 AAC Blackout

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dellet
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Re: PSA 16” 300BLK issues

Post by dellet » Fri May 24, 2019 12:46 am

jps1542 wrote:
Thu May 23, 2019 1:36 pm
These are loaded at 2.1 COAL. I could possibly do a tad longer, but I would be past the cannelure. I have noticed riding the bolt slow and watching it is the rounds to like to jump from the magazine. That being said, I have yet to recreate the malfunction hand cycling the gun. On the spring/buffer, I’m aware about geisseles warning in regards to it and sub Sonics. Yet I have not experienced any issues of any kind with subsonics. I have not tried a h2 or h3 Buffer yet because I don’t have any lying around. Almost all my other AR15s are rifle gas for 223(3 gun rifles). My other blackouts are all standard carbine springs and buffers. But they are also 7-11” barrels.
You said that you first thought was over gassing. I’m agreeing with you that is likely. Seating longer might help that, but you will still be over gassed. You have not mentioned a suppressor, adding that to the mix will make it even worse.

By design, it’s pistol gas, H2 buffer. Carbine gas, carbine buffer. 16” pistol gas was never marketed by AAC because of too many feeding problems with supers, unless an H3 buffer was used, and that created problems with subs.
300 Blackout, not just for sub-sonics.

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