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Eric
18 June 2009, 20:40
After spending some time with the CMMG .22 Cal conversion kit (http://www.weaponevolution.com/forum/showthread.php?t=1300) I'm convinced they are a viable option for training, introducing new shooters to the system, plinking and just having fun. While they don't exactly duplicate the feel and function of the real thing they have their place.

So, what do you all think? Does anyone have some time behind a similar setup? Do you think conversion kits or a dedicated .22 upper is in your future?

rob_s
19 June 2009, 02:53
With all of the .22 conversion interest lately due to the ammo situation I've been contemplating adding an article about them to my site. Here's my take, based on previously owning a dedicated upper (a DPMS of all things) and observing several of our shooters that spend time training with them.

First is the issue of conversion vs. dedicated upper. IMHO the upper is the only way to go for a few reasons:
1) Bore. a .22 LR is typically .223, while an AR is typically .224 (IIRC). I don't know that the .001 makes that much of a difference, but I do believe that it will cause less desirable accuracy.
2) Twist. 5.56 rifles are generall 1:9 or 1:7, with 1:12s still floating around out there. Most dedicated .22 LR rifles are in the 1:14 to 1:16 range. Again this can cause accuracy issues shooting a .22 in a 1:7 twist.
3) Zero. The .22 is not going to shoot to the same POI as the centerfire through the same barrel (especially given #s 1 and 2 above). This means sight/optic adjustments whenever you switch back and forth. Yes, you can write down your # of clicks in either direction and adjust the sights every time you shoot, but I find this to be less than ideal.
4) FCG. Some rimfire kits benefit from a lightened hammer and/or spring. While the dedicated upper alone won't address this, putting the dedicated upper on a dedicated lower will. Yes, you could do this with the drop-in kit but that kind of defeats the purpose of the drop-in kit to begin with. Having a dedicated rifle means you can tune the FCG to the caliber if needed.

In terms of training benefit, I think the .22 ARs have a place but I think there are limits to their benefits and can be detrimental if used incorrectly. Where I think they shine are:
1) Marksmanship. Sight picture and trigger control, provided that they are the same or similar to your centerfire rifle, can be identical or close enough to be a great way to practice these skills for much cheaper and/or on ranges that don't allow centerfire rifles.
2) New Shooters. Having a rifle that, for all intents and purposes, functions in the same way as the centerfire version but does so with far less recoil and noise is a great way to introduce new shooters (especially women and children) to the AR. Once they get comfortable with the .22 it is very easy to just swap out an identical centerfire rifle and make an almost seamless transition.

Where I think they have limitations or can be detrimental are:
1) Speed. It is very easy to shoot a .22 AR quickly. Controlled pairs, hammers, engaging multiple targets, etc. are all done very quickly with the .22 due to the non-existent recoil. The problem here is that the muscle-memory doesn't carry over to the centerfire gun that actually does have some recoil. If you train too much with the .22 in this way it can have a negative effect on your skillset with the primary centerfire gun.
2) Reloads. The .22s don't lock back on the empty magazine, and the few that do drop the bolt when the magazine is stripped negating the benefit of having it lock open to begin with. This means that the emergency reload is done differently with the .22 than with the centerfire gun. Even if you're not intentionally practicing emergency reloads with the .22, if you allow the gun to run dry you're again building in muscle memory to reload the gun a certain way and that way is less than ideal with a centerfire gun.
3) Malfunctions. Malfunctions are not only more common with the rimfire guns but, due in part to the fact that the bolt doesn't lock open, are cleared in a different way. It should be obvious why this is bad.
4) Trajectory. A 40 grain .22 bullet is going to have a different trajectory than a 77 grain 5.56 bullet. This means that one has to be careful as to sighting distance as it affects hold-over and -under so that bad habits aren't ingrained. POA/POI issues should be worked out with the centerfire gun and every effort should be made to zero the rimfire in a way that causes it to mimic the holds as much as possible with careful attention paid the ranges at which this can work. If POA/POI can only be mimiced out to 25 yards then that's the limit at which you should "work" with it.

sjohnny
19 June 2009, 07:58
1) Marksmanship. Sight picture and trigger control, provided that they are the same or similar to your centerfire rifle, can be identical or close enough to be a great way to practice these skills for much cheaper and/or on ranges that don't allow centerfire rifles.
2) New Shooters. Having a rifle that, for all intents and purposes, functions in the same way as the centerfire version but does so with far less recoil and noise is a great way to introduce new shooters (especially women and children) to the AR. Once they get comfortable with the .22 it is very easy to just swap out an identical centerfire rifle and make an almost seamless transition.


A friend of mine (USAF) had a .22 conversion for his personal AR. When folks were having trouble qualifying he would take them out on his own time and have them shoot the hell out of his AR with the .22 conversion in it (he had a personally owned Beretta with a .22 conversion also and would do the same drill with it). After getting familiar with the .22 AR he would switch them over to 5.56 (sometimes with a can at first if the noise was a problem). After spending a little time with the .22 nobody ever had any problems qualifying with the real deal. I'm interested in getting a conversion or maybe a dedicated .22 upper at some point (I haven't even built the rifle yet) and would ideally like to have .22 conversions or an identical/similar gun chambered in .22 for all of my guns.