**UPDATE**Request help to diagnose a bad malfunction

**Alpine2k3** · 09-29-20, 18:14

I would check the bolt to make sure it’s not damaged. That barrel extension looks awfully rough.

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**Serpico1985** · 10-02-20, 12:39

No bolt damage, may just be the lighting giving that impression.

UPDATE 10/2/2020

Got to the range today and was able to test the rifle in the new upper. Remember I swapped the ADM upper for a SOLGW upper. Results are as follows. Keep in mind last time the gun was failing to feed every other round with pmags and 20round colt mags

-With the new upper (SOLGW) we made it through about 10 rounds of the duty ammo from the pmag before we got the same malfunction as last time:

-So we swapped the Geissele super 42 buffer and spring for a standard carbine buffer and spring, topped off the mag with more duty ammo and blazed through the entire mag with zero issues.

-Then we put the Geissele super 42 buffer and spring back in and replaced the LMT enhanced BCG and enhanced bolt with a standard mil-spec BCG and bolt. Loaded back up with duty ammo and shot the mags empty, no problems.

-Finally we shot his upper with his LMT enhanced BCG and enhanced bolt on a SBR lower with an A5-2 buffer and blazzed through a couple mags of duty ammo without issue.

My best guess is that the combination of the super 42 buffer and spring (noticeably stouter than the standard carbine spring and A5 spring) when combined with the LMT enhanced BCG and enhanced bolt (which reduces gas pressure vs a standard BCG) was not giving enough gas to fully run the gun. Which is why replacing one or the other with a standard unit let the gun run. Also, best guess for the barrel extension overhanging the ADM upper's feed ramps exacerbated the original feeding issue which is why it was failing every other round vs going 10 rounds today without issue.

Am I drawing conclusions to fit my assumptions? Probably. But whatever, the gun is running now with all his ammo in all his mags so we'll call it gtg.

Thanks