I have a Spike's 22 upper that I use for some training. I mainly use it for trigger time since it is set up similar to my primary carbine. You can use the 22 upper with good effect on some drills but others you should stay away from. Anything with recoil management is a non-starter. Trigger control and marksmanship are the big ones that you can work on. Additionally, you can work on your transitions to the handgun from the carbine. That is my 2 cents.