Re: AR 22lr upper
At one point I did go down the dedicated upper road. Keep in mind the upper is a compromise so you can shoot the 22LR. Spikes uppers are top of the line, excellent customer service and fast turnaround if upper needs to go back for repairs.
Some uppers may require fine tuning to run the ammo that you are using. Reliability of a regular AR or 10/22 you may not find it with the dedicated upper.
For me my CZ 452 Varmint and my upgraded 10/22, they work, no fine tuning, they will shoot anything I feed into them, this works for me.
You will have a hard time if you are looking for a tack driver out of a dedicated upper.
alexander66