Colt AR-15 .22LR Conversion troubles

[epa223]

Hello everyone,
My buddy called today to let me know his recently purchased conversion wouldn't lock the hammer back to fire another round. It would however, move back enough to pick-up and chamber one. He tried this conversion on an SP1 Carbine (with AR hammer) and an M16A1 retro build (semi-auto with a modified M16 hammer) and it malfunctioned in both. He tried his Army M261 and his Air Force in both without any problems. He used the same ammo in all 3 units (Federal 40 grain lead round nose). He had 5 rounds of CCI Mini Mags laying around and the first 4 worked fine with the 5th jamming (he believes due to the longer case, apparently). The only thing I could offer for him to try was a different Colt magazine (that was the only thing he didn't try). Anyway, if anyone here can give me some advice regarding this issue, I'll pass it on and my buddy will certainly be thankful. Thanks!

[joem]

You didn't mention the brand name of the conversion. I bought a Ceiner conversion and it works perfectly right out of the box.

[epa223]

The brand is COLT (as in the title) ;)

[joem]

You might try a really good cleaning and seeing if it mechanism moves freely while it's out on the bench. Maybe a little lube ot a metal burr is inside it.

[epa223]

Here's some history on this. As you may or may not be aware, the Colt conversion has a roll pin that is actuated by the charging handle to pull back the bolt and chamber a round. However, for some goofy reason, Colt placed this pin about 3/8" too far back on the bolt to force the charging handle closed when chambering a round. My buddy didn't like this and modified the charging handle so that it would close when the bolt did. The first thing I asked him was whether or not his modification was the problem. He said "no". My guess was that something involved with the magazine may be creating a bit of drag on the bolt and thus not allowing it to move freely rearward. As far as cleaning, the unit, although used, looked almost new and apparently operated smoother than the Army and Air Force units (according to him). He hasn't called back yet so I don't know if he's found the problem or hasn't had time to look yet. I'll keep you informed. Thanks.

[epa223]

Here's an update. The second mag didn't change anything in the SP1 but he did have a few 2-3 round bursts in the A1 retro (presumably slam fires from the before mentioned issue). Not sure why the AR hammer won't slam-fire and the converted M16 will? Anyway, he's going to take some time off of this and try to figure something out. I think I'll try it in a couple of my rifles the next time I go out there. If it still doesn't work, he'll probably try to sell it. He hates to do it especially if there really is a problem with it but it would appear nobody else has a problem with these units so maybe its just his "luck".

[Dienekes]

FWIW I had a CMMG conversion unit. It never ran well, and in some mysterious fashion gave me a bulged barrel. Exact reasons forever unknown, but bulged nonetheless. Replaced the barrel with a lightweight one which I preferred anyway, and went out and bought a purpose-built S&W 15-22.

I now have over 3K rounds through the S&W with only the occasional ammo-related misfires common to all .22 LRs; best gun I have bought in years and nonstop fun.

[BruceHMX]

I think it's just all the variations in 22LR ammo. I have a CMMG unit that I shoot in my Bushmaster M4 all the time. I keep it clean and lube it with a good silicon spray before shooting. I have 20 magazines. The boys last year put 3 Federal bulk packs through it in a day. That's over 1600 rounds. We had maybe 10 FTF or misfires total. Between the differences in rifles and units you hope you get one that shoots and shoots right. I have two Colt Ace units. The one with fixed sights will run all day. The 80's version with adjustable sights might get 100 rounds out before a cleaning is needed. I gave up on my SIG 210 22 unit years ago. The only 22 ammo that with function great out of it is CCI Stingers. Pricey and too much wear and tear on the unit.

I would try the unit in other AR15's and see what results you get. Make sure the rifle is clean as well as the unit and use a good silicon lube.

[joem]

My Ceiner conversion runs either semi or full with no problems.

[epa223]

I got the chance to do a couple hours of shooting with my buddy this past Sunday with the express objective of finding out the trouble he's having. Long story short... Nothing he used (rifles, ammo or magazines) worked. Low and behold, he tells me he has only been using ammo from his recently purchased brick of Federal/American Eagle. I had 300rds of 1980's vintage Federal Lightnings with me and told him to give them a try. They worked. All 3 conversions and both rifles worked perfectly. Although I'm sure I asked him if he tried different ammo (he also just bought a brick of Federal Champion .22's), he didn't. So, after all this, it would "appear" as though it was an ammo issue. I say "appear" because he traded me his remaining 400 rounds of American Eagle for my Lightnings and just before packing up, I proceeded to shoot 50rds (5 mags) through my M261 without a single problem. Go figure???

[RED]

All .22 conversions can be finicky. My J. A. Ciener conversion functioned great in my NFA registered M16A1 on full auto as well as semi. The problem is the twist in 5.56 barrels is way too fast and will lead up the barrel most ricki tiki. When that happens about the only easy way to fix it is to fire a few .223 rounds to "clean" the barrel. What that does to the pressure curves and the gas system is problematic. The dedicated .22LR upper is the answer. I have two of the CMMG dedicated uppers and they run on every thing I have put in them as long as you keep them relatively clean. In fact I prefer shooting the dedicated CMMG over my 10-22 because it is less finicky with hi cap mags.

[joem]

Red, do those CMMG uppers work with your M16A1 on FA? I have found the same problems with mine.