Bolt group

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gunnery32
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Bolt group

Post by gunnery32 » Mon Jul 06, 2020 5:36 pm

Hi, new to the forum. Already had ar15 lower (spikes tactic in .223l). Bought a 300 blackout upper (palmetto armory). Everything fits together fine, but when I pull the charging handle back to chamber a round...the bolt group only goes back about 1 1/2 inches. So, not nearly enough to chamber a round. Have taken apart and put back together a few times to see if all is in order. Not making any progress. Any suggestions would be welcome.
Thanks

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20X11
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Re: Bolt group

Post by 20X11 » Mon Jul 06, 2020 7:42 pm

Does the BCG go all the way back without a magazine in the rifle?

gunnery32
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Re: Bolt group

Post by gunnery32 » Mon Jul 06, 2020 7:47 pm

Same problem with or without mag. Also removed buffer and spring (along with detent/spring) and the bolt group retracts all the way back.

20X11
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Re: Bolt group

Post by 20X11 » Mon Jul 06, 2020 7:54 pm

ok, sounds like a bad BCG...does the groove on the bottom of the BCG run the full length, or did it get "short machined"?

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dellet
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Re: Bolt group

Post by dellet » Mon Jul 06, 2020 8:07 pm

If you changed out only the upper, I would try the BCG from the 223 upper.

One thing to look at is the vent holes in the forward part of the carrier, or any other holes. I have seen where the pawl on the forward assist jams into these holes. You may see a mark there on the one that jams. If that happens you might need to replace the forward assist.

If you changed anything else it would be good to know also.
300 Blackout, not just for sub-sonics.

gunnery32
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Re: Bolt group

Post by gunnery32 » Tue Jul 07, 2020 11:09 am

Well first, thanks for the suggestions. I tried the other bcg into it but with the same problem. In looking at the two bcg’s side by side....they look the same as far as grooves etc. No scratch marks etc. I’m kind of at a loss. Will contact Palmetto state today.

gunnery32
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Re: Bolt group

Post by gunnery32 » Tue Jul 07, 2020 11:34 am

Progress, I mounted the PSA upper on another lower (Franklin Armory). Functions fine. So now, problem is with the lower I originally mated it with (SpikesTactical). Any suggestions on what to look for on an AR lower which won't let the bolt carrier group go far enough back?

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Re: Bolt group

Post by 20X11 » Tue Jul 07, 2020 11:45 am

How far up does the buffer retainer stick up into the end on the tube...compared to the lower that works?

gunnery32
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Re: Bolt group

Post by gunnery32 » Tue Jul 07, 2020 11:52 am

I put them side by side...but they both protrude the same amount.

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dellet
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Re: Bolt group

Post by dellet » Tue Jul 07, 2020 12:26 pm

It's a bit of a hassle but you can put it together without the buffer retainer.

Have you tried

pushing the BCG into the buffer tube without the upper, spring and buffer installed?

Holding the bolt release in the down/release position and pull the bolt back?
300 Blackout, not just for sub-sonics.

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