.22 LR conversion kits. Are they safe?

**Claymation** · 05-04-11, 13:02

Gentlemen - I recently sold my first born child and purchased an LMT MRP middy. I'm interested in purchasing a .22 LR kit so my second born son can shoot the AR, and also save on ammo costs.

I've heard some horror stories about .22 kits damaging the barrell of AR's. Obviously with the kind of money I spent on my AR, I'd rather spend the extra on ammo than damage my LMT barrel. Are the .22 kits safe? If so, are there any that guarantee they won't damage my barrel? Which ones do you recommend? Cheaper than Dirt sells one for $129...is it crap? Thanks.

**The Cat** · 05-04-11, 13:13

I can't speak for the newer kits, but I have an old Colt kit that I've put several thousand rounds through without any trouble.
Its only downsides are that it only has one 10 round mag, and it's finicky about ammo that it likes.

I can't see how they'd hurt the 5.56 barrel, other than maybe leading it up a bit. I use copper coated ones though and that minimizes the leading.

**Dienekes** · 05-04-11, 19:49

Here's a story for what it's worth. I bought a CMMG conversion unit about a year ago, and used it in my M4gery fairly regularly with Federal American Eagle 38 gr. HVHP ammo. That's whaT I've bought in bulk over the years and used with good results in quality guns. I get the very occasional misfire but not many and have stayed with it.

When I used the conversion unit it was usually about 40 rounds in single shot drills. I would have occasional failures to extract and the POI was about 4" lower out at 50 yards. Accuracy was about 2" at that range, and as long as I took those things into account I was fairly satisfied with it. I cleaned the chamber and bore with brush and patches after each range session.

The last time I had it out was in January and I was doing doubles on the timer. I was also getting more failures to feed and extract than usual so I was either busy shooting or clearing malfunctions. I was checking the (reduced) target and pasting each two rounds, and on one occasion I noticed one normal hole and one rather smaller one on the target. Thinking this odd, I broke the gun open and pulled the BCG out to check the bore. It looked clear, so I put it back together and continued shooting. The gun ran normally for the rest of the session.

When I got home I noticed that the cleaning rod and brush felt odd in the area of the FSB; same with patches. I used some JB cleaning compound on the bore which got it nice and clean but the odd feel remained, and I thought I could see a shadowy area down there. When I took it to a gunsmith I use he took one look and pronounced the barrel bulged.

The upshot was that I ordered a new "pencil barrel" and installed that on the carbine along with a new bolt and cam pin, and test fired it recently. When I tried to remove the FSB from the old barrel it took a lot of force. When I miked the area where the alleged bulge was I found it to be .006 larger for about an inch. When I get around to it I will have it sectioned there to see exactly what I've been dealing with.

As to exactly what happened or why, I really can't say with certainty.
What I do know is that I discontinued using the conversion unit and bought a S&W 15-22 to replace it.

You're free to draw your own conclusions.

**Suwannee Tim** · 05-04-11, 20:49

Spikes makes a 22 LR barrel to fit the MRP, I have one and am very pleased with it as well as the Spikes 22 device. Make sure you get a magazine loader. Well worth the ten bux.

**shadow65** · 05-05-11, 09:55

Spikes pulled the ST22 and the conversions off the market due to quality of supplied parts, according to Spikes.

I have used the CMMG conversion quite a bit and have not found any evidence of an issue.
The new Evolution kits have many features the old ones did not, including live round extraction.
Most feeding problems occur when the kits are taken apart. If the rails get bent it can have all sorts of problems. Unless a firing pin or extractor needs to be replaced, it is advised not to disassemble the kit.

When I am finshed shooting .22 I pull the bolt, run a boresnake down the barrel while it's still warm, fire 5 rounds of 5.56 and properly clean the upper when I get home.

Be aware that the kits you see at CTD and CDNN are old discontinued kits, not the new Evolution and do not have the features and up grades.
The CMMG Evolution stainless with live round extraction, cotter pin holding the firing pin, push pin holding the extractor, and forward assist is the best, most reliable on the market. I've tested these over the last year.
The ultimate is the India which has a brass locking lug that locks into the chamber of a 5.56. Expensive though. You can buy a dedicated upper for a little more.

A dedicated upper will definetly give you better accuracy and remove any concerns about shooting .22 through the 5.56 upper. And with the price a dedicated upper can be bought, it's a better option for me.
Dave

**Suwannee Tim** · 05-05-11, 18:12

Originally Posted by shadow65

Spikes pulled the ST22 and the conversions off the market due to quality of supplied parts, according to Spikes........Dave

Indeed as they are no longer listed on the Spikes web site. I have been very pleased with mine, especially the 22 LR MRP barrel. I guess it's a bit of a collectors item now. I'll have to take better care of it. Maybe even clean it. I've got maybe 8K rounds through it, never cleaned it. I've blown it out with a can of air a couple of times. I did have some fun with it last Friday. I let some guy go on and on about how important it is to keep an AR spotless, especially the trigger. Then I separated my 22 and presented it for the consideration of attendees of the lecture.

'Cause it is feelthy!

**austinN4** · 05-06-11, 04:22

Originally Posted by Claymation

I've heard some horror stories about .22 kits damaging the barrell of AR's.

Someone please help me understand how just using a 22LR conversion kit would damage a barrel? I can see how not cleaning a serious lead build up might, but not just the simple act of using the kit.

BTW, I have multiple thousands of 22LR through my 5.56 barrel with no problems at all, either with the kit or to my barrel. I am using the original CMMG kit. At the end of my sessions I just run a bore snake and some 5.56 through my barrel and call it good.

**Suwannee Tim** · 05-06-11, 05:55

If you shoot lead bullets in a barrel fouled by copper it is possible for heavy leading to occur. If you then switch back to jacketed bullets you can damage the barrel when the jacketed bullet runs over the lead. It is a well known fact among cast bullet shooters that copper fouling promotes leading. Users of 22 converters should be aware of this. If I was shooting a 5.56 barrel with 22s, I would run a patch down the bore with a rod, not a bore snake and not an Otis. You can feel heavy leading as well as see it. It looks like gray streaks.

**usmcvet** · 05-06-11, 06:42

Good info here guys. For those of you using a dedicated .22 upper what are you using? I'm trying to decide between a conversion kit and a 15-22 now a dedicated upper might get into the mix.