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Posted: 8/14/2011 1:49:02 PM EDT


I have a CMMG .22 caliber conversion in a standard semi-auto M4 rifle with M4 stock, using Blackdog mags.

Ammo: Federal Bulk and CCI Minimags.

This is what is happening,

1) Chamber a round and fire it.

2) The spent round is ejected.

3) The next round is stripped and fed into the chamber 3/4 of the way.

4) The bolt does not fully seat the round in the chamber.

It's almost as if there is not enough recoil energy to return the bolt all the way back.

Any ideas on how to trouble shoot it or recommendations?
Link Posted: 8/14/2011 2:18:47 PM EDT
Check out the top of the right side feed lip. Is the bolt rubbing on it? It did on the CMMG .22 conversion kit with black dog magazines in my son's AR15. We took a knife (pocket knife right there at the range and slowly/lightly scraped the top of the right side feed lip on a couple of new black dog magazines until the bolt would smoothly/completely go forward each time it chambered a new round from the magazine.

Don't cut the plastic off, hold the knife blade perpindicular to the top of the feed lip - or, if you're at home, try some sand paper or a file - but go slow and don't take off more than necessary to stop the bolt from dragging across the top of the lip.

At least that was what was happening with my son's conversion kit/rifle.

Good luck with yours, if that's not it I can suggest only one other thing that I do to my new .22 conversion kits. I use carb. cleaner to remove all the lube and the smear some lapping compound on the rails and work the bolt back and for 50 to 100 times, spray the lapping compound off with carb. cleaner and then lube it up and shoot it. The lapping compound just polishes/smoothes out the bolt to rail rubbing surfaces quicker.
Link Posted: 8/14/2011 3:22:25 PM EDT
Some Black Dog Mags have feed lip interference. Usually, you will see empty cases get stuck in the charging handle/top of bolt assembly.
I would buzz the chamber. Put a .22 bore brush in an electric drill. Put oil on it and run it in the chamber for 30 seconds.
The helps smooth/polish the chamber.
Does the bolt go forward when the mag is not inserted?

Take the conversion out and make sure there is no binding on the rails. Just move the bolt back and forth, checking for binding.
Dave N
Link Posted: 8/14/2011 3:42:36 PM EDT
Thanks for tips. I will try the mag alteration and buff the chamber.

Yes, the bolt goes home without the mag inserted.

I am going to use this on the feedlips.



























Just kidding!
Link Posted: 8/14/2011 4:01:39 PM EDT
Can you drop a round into the chamber without anyresistance and will it fall out on its own? Is your chamber clean?
Link Posted: 8/14/2011 4:08:19 PM EDT
One more issue I have seen is because of varying tolerances, some Bolt Catches are slightly high and the bolt can rub on the top of it. A little filing on the bolt catch will solve that.
Dave N
Link Posted: 8/14/2011 4:10:16 PM EDT
If you do a google search on ciener polishing - there is a post on the uzi forums that is great on how to polish these to be more reliable.. One step was to polish the inside of the chamber so that doesnt happen..

Brian
Link Posted: 8/14/2011 4:28:30 PM EDT
Have you tried the CCI AR Tactical .22 ammo? http://www.midwayusa.com/viewProduct/default.aspx?productNumber=337297

My .22 setup used to be a pain. It would run great then do just what your's is doing. I bought some of this ammo, and have since run a whole box through with no problems. Might be an even easier fix.
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