New Magpul UBR-2 bolt not locking back on PMAGS

[jerrysimons]

What is the finish or texture inside the UBR receiver extentsion like?

[556Cliff]

What is the finish or texture inside the UBR receiver extentsion like?

Mine is very smooth.

[pezboy]

I got mine in a little while ago but haven't shot it yet. I believe the inside length was less than my Vltor A5 receiver extensions. I'll see if I can get comparison pics later.

[RobertTheTexan]

I'll test mine out today. I haven't used a pmag with it. The lancer has been flawless.

ETA: After testing, 30rd gen 2 and 10-20-30 round gen 3 pmags work well with mine with manual cycling. I'm running the A5 system.

Thx for the follow up Fledge. What weight buffer is in your tube? Also assuming you're running the standard A5 spring or rifle spring?


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[pezboy]

The one A5 extension I compared to the UBR 2.0 was less than .010" deeper. That's within the variance for length just based on where the threads start on a carbine receiver extension.

[556Cliff]

I just measured the inside length of my UBR Gen 2 extension and it was 7 and 3/4 inches.

7 and 3/4 inches is the same as my Magpul 10 position extension and my Vltor 6 position RE-10/A5SR extension.

[fledge]

Thx for the follow up Fledge. What weight buffer is in your tube? Also assuming you're running the standard A5 spring or rifle spring?

Vltor spring. A5H2 buffer.

[RobertTheTexan]

Vltor spring. A5H2 buffer.

Same as mine. I've got some free time Friday to test the mess out of my UBR'd SBR. I'll bring some spare buffers and different mags and see if I can't narrow down the issue(s).


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[RobertTheTexan]

Has anyone discovered anything with this potential issue?
I'm back stateside and going out in the morning to do some serious testing. I'll bring a couple of springs and different weight buffers with me. I'll also bring the 62gr ammo I've shot a lot of as well. Not sure what else I can do? Swap BCG's?


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[M4Fundi]

Did not mean to go MIA on this, just I don't want to keep this issue unnecessarily stirred up with speculation while I'm actually getting to the bottom of it with action and then some results based on evidence. For my particular situation Magpul, Noveske and VLTOR are all being helpful. I don't want to say, "well so far or I think.." I will hopefully know the next range trip what the problem is. I honestly thought this was going to be easily solved and not take so much sleuthing to figure out.