300blk pistol failure to feed/extract

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Heygorgeous
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Posts: 2
Joined: Fri Aug 13, 2021 8:33 am

300blk pistol failure to feed/extract

Post by Heygorgeous »

Hi all, hoping someone can help me troubleshoot this issue. Just built a 300 blk AR pistol but the problem I’m having is I can’t seem to chamber a round from the closed bolt position by hand, ie: combat reloads.

It only feeds the first round reliably when using the bolt release AND brass ammo AND the first round is on the right side of the stack. Subsequent rounds are cycled ok while firing so I don’t think it’s short stroking. It’s a bitch trying to chamber the first round of steel case. Have to bang the mag on my foot a bunch and make sure it’s seated just right.

I only shot about 30-40 rounds of supers through it so far. I’ve tried sellier and bellot 147gr fmj (brass) and 145 gr wolf (steel case). It seems to like brass better and prefer to feed from the right side of the stack in both usgi and pmag gen3 mags. Empty mags hold bolt open reliably.

It also doesn’t extract live rounds sometimes. I’ll release the mag and pull the charging handle but find that the round is still in the chamber sometimes and have to prod it out with a rod.

Here’s the build:
-BCA 7.5” barrel 1:8 parkerized
-pistol length gas tube, .750 low profile gas block
-Anderson upper w forward assist
-17D lower with mil spec lpk
-mil spec CH and nitride BCG
-pistol buffer tube with 3oz buffer

TLDR:
-gun no work when pull charging handle
-me mad
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der Teufel
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Joined: Mon Nov 19, 2018 2:58 pm
Location: Central Texas

Re: 300blk pistol failure to feed/extract

Post by der Teufel »

I'm not an expert at all, but if I understand correctly you're having difficulty chambering a round when you've inserted a new, fully loaded magazine into the weapon while the bolt is closed.

I can't say definitively what is causing the problem, but that can be an issue. The fully loaded magazine doesn't allow itself to be fully inserted. The top rounds hit the bolt and stop the magazine from properly seating. One solution is to lock the bolt back and then tap the magazine into place. If that fixes the issue, then you know the cause. Whether it's an inherent weapon issue, or a magazine issue, I cannot say.

Generally speaking, the bolt should lock back when the magazine goes empty. You can then insert a new magazine and afterwards release the bolt. That shouldn't cause any problems. So, in a combat reload situation you should not experience the problem unless I'm missing something (very possible).
"A man with a gun is a citizen. A man without a gun is a subject." — John R. Lott
Targeter
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Posts: 2
Joined: Mon Aug 16, 2021 5:31 pm

Re: 300blk pistol failure to feed/extract

Post by Targeter »

Sounds like a magazine problem. Did you try Magpul 300BLK specific magazines, or GI mags with 300BLK followers?
Heygorgeous
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Posts: 2
Joined: Fri Aug 13, 2021 8:33 am

Re: 300blk pistol failure to feed/extract

Post by Heygorgeous »

der Teufel wrote: Sun Aug 15, 2021 12:16 pm I'm not an expert at all, but if I understand correctly you're having difficulty chambering a round when you've inserted a new, fully loaded magazine into the weapon while the bolt is closed.

I can't say definitively what is causing the problem, but that can be an issue. The fully loaded magazine doesn't allow itself to be fully inserted. The top rounds hit the bolt and stop the magazine from properly seating. One solution is to lock the bolt back and then tap the magazine into place. If that fixes the issue, then you know the cause. Whether it's an inherent weapon issue, or a magazine issue, I cannot say.

Generally speaking, the bolt should lock back when the magazine goes empty. You can then insert a new magazine and afterwards release the bolt. That shouldn't cause any problems. So, in a combat reload situation you should not experience the problem unless I'm missing something (very possible).
Not fully loaded - even with 5 rounds. And combat reload as in dropping a mag with a few rounds left and replacing with a fresh one.

Targeter wrote: Mon Aug 16, 2021 6:17 pm Sounds like a magazine problem. Did you try Magpul 300BLK specific magazines, or GI mags with 300BLK followers?
Yeah I tried lancer 300s and it seems to work well. New to 300blk and heard most 556/223 mags work with it but turns out it’s just finicky. I’ll just stick with 300blk specific mags from now on
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dellet
Silent But Deadly
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Joined: Fri Nov 30, 2012 1:25 pm

Re: 300blk pistol failure to feed/extract

Post by dellet »

Sounds like two different issues.

Easiest is the extraction issue. If the round won't fall out under it's own weight,
I’ll release the mag and pull the charging handle but find that the round is still in the chamber sometimes and have to prod it out with a rod.
You have a chamber or ammo issue.

A good clean and polish of the chamber might solve that issue, if not you need to measure the ammo, most likely the neck diameter and make sure it's in spec. If the ammo measures correct, send the barrel back.

The feeding has more possibilities.

Since the bolt releases and feeds ammo when you manually drop the bolt catch, start there. Make certain when you insert a loaded magazine that that the drops down when you pull the charging handle back. A good guess would be that it is not. Since you say that a loaded magazine is hard to insert, it may be that the interference is the bolt catch. If it not dropping down, it will block the bolt from pushing the loaded round forward.

You could remove the catch and if the magazine inserts correctly and rounds feed with the charging handle, you know where to start looking.
300 Blackout, not just for sub-sonics.
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