Aero Precision.308 not locking open on final round.

[SVTSkippy]

Hello-

**Problem**
When guns are fired on single round the bolt does not catch open.  When multiple rounds are fired the first ejects and the next jams.  When sliding the bolt back by hand it easily locks in place.  Adjustable gas block is 15 clicks open (even tried 20).

 

**Builds**
Parts in common

Aero Precision M5E1 Lower, upper, handguard, Aero Pecision Adjustable gas block, AP gas tube, AP M5 Rifle buffer tube, spring and buffer. AP lower parts kit, Toolcraft BCG. Two different Gen 3 10rd PMags.

Spring 38 coils, 12.5” Buffer length 5.3”.

Ammo 150 grain Norma and 150 grain Win Power point. 

Parts Different 

Build A

Criterion 20” Barrel, Geissele SSA-E Trigger, Magpul PRS Gen 3 Stock

Build B

Faxon 18” Barrel, RIse Armament RA-535 Trigger, PSA A2 Stock.

 

Since they are both doing it I am figuring it should be one of the items in common or the fact I built both…. We took the gas tube and block off and made sure air was flowing and readjusted and had same issues.  Before I start just throwing parts at them I would like some ideas.  Typing this on my phone in the deer stand so hopefully readable.

 

Thanks in advance.

[jim3326]

First best guess would be short gas tube or undersized gas port, maybe both. More info needed. Check out the 'Waterboarding' thread.

 

Edited December 16, 2022 by jim3326
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[shooterrex]

Bet your gas port is too small.

[308USK]

What @shooterrex said!  Gas port is too small...and/or buffer spring & weight are incorrect.

[SVTSkippy]

We left the breach open to have pressure on the springs over night.  They work perfect now.