Bolt Lock Back Issues... Not Sure Why?

[MistWolf]

Brand of bolt catch?

It was a cheap generic bolt release.

The way I read this, you tested each variable separately. This is the way to trouble shoot any problem. The only problem resulted in the use of Pmags, either generation. On the other hand USGI did work. Shouldn't you be looking a those pmags more closely?

Pmags and GI mags interface with the bolt catch differently. When the catch is damaged or becomes misaligned, often one type of mag will work while another will be problematic.

[simplefolk]

I never knew this, thanks so much for sharing.

[arptsprt]

Because everyone was on pins and needles about this, here’s an update.

Popped out the bolt catch for inspection and cleaning. Cleaned, changed the spring, and reinstalled. Nothing seemed whacky but...

Also noted the bolt failed the gas ring test. A little surprised because this bolt/BCG only has about 1000 rounds through it. Replaced the rings.

Shot several rounds today and had zero issues. Good lock back on all mags. Issue resolved.


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[26 Inf]

Good to hear, thanks for the update.

[Iraqgunz]

Was it also a BCM BCG?

Because everyone was on pins and needles about this, here’s an update.

Popped out the bolt catch for inspection and cleaning. Cleaned, changed the spring, and reinstalled. Nothing seemed whacky but...

Also noted the bolt failed the gas ring test. A little surprised because this bolt/BCG only has about 1000 rounds through it. Replaced the rings.

Shot several rounds today and had zero issues. Good lock back on all mags. Issue resolved.


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[arptsprt]

Yes, it is also a BCM BCG. Something I need to be aware of?

Was it also a BCM BCG?

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[Iraqgunz]

Nope. Just wanted to know as I didn't see BCG mentioned.

Yes, it is also a BCM BCG. Something I need to be aware of?






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[cutter_spc]

Because everyone was on pins and needles about this, here’s an update.

Popped out the bolt catch for inspection and cleaning. Cleaned, changed the spring, and reinstalled. Nothing seemed whacky but...

Also noted the bolt failed the gas ring test. A little surprised because this bolt/BCG only has about 1000 rounds through it. Replaced the rings.

Shot several rounds today and had zero issues. Good lock back on all mags. Issue resolved.


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Maybe I read it wrong. Weren't there two complete uppers that were having the same issues? Both bolts had ring issues? This whole thread I have been wondering about the mag catch, somethings allowing G.I. mags to work but not Pmags. Wouldn't worn rings fail on both mag types?

[arptsprt]

No. Only one upper with the issue - wouldn’t lock back on PMags, would lock back on USGI.

Not sure if the worn rings had anything to do with. I hadn’t even thought to check the rings because of the low round count and lack of any symptoms of worn rings. Caught it during a more thorough inspection before shooting yesterday.

Worn rings and a minor issue with the catch probably combined to cause the issue. As was said earlier, PMags have a little different geometry. Probably just one of those strange combinations of a few small things. Sometimes it happens.

Maybe I read it wrong. Weren't there two complete uppers that were having the same issues? Both bolts had ring issues? This whole thread I have been wondering about the mag catch, somethings allowing G.I. mags to work but not Pmags. Wouldn't worn rings fail on both mag types?

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