I have a drop in CMMG .22lr conversion kit in a 16inch carbine (my backup). It works well for its intended use.... I use it for muscle memory transition work(left right side barricade transitiions, awkward shooting positions at relatively short distances 35yds or less. It is not very accurate (3-4 inches at 50m)in my Colt flat top due to difference in bore to bullet diameter. My STC 10/22 will shoot 1inch at 100y. I used it for about 500rds before Ft Benning last year, and the interior was really dirty. Then I realized that I didn't really need to tap the gas as the unit is straight blow back, so I removed the gas block and tube, and covered the hole with a stainless screw clamp. Will be using it again this year as we ramp up as Dec gets nearer. I really stress the visualization part of practice, but rely on live fire practice on steel reactive targets for immediate feed back. regards Les