It has more to do with the barrel twist rate than anything else.
A "standard" twist rate for a 40 grain .22LR bullet is 1 turn in 16". Most AR barrels nowadays are 1 in 7 or 1 in 9 (there's some 1 in 8 out there and varmint style and older barrels may be 1 in 12 for use with lighter bullets). Those faster twists will overstabilize the bullet and open up your groups a bit. I've read of folks using those conversion kits getting only so-so accuracy at best.
However, there is one other option.
The Aguila SSS 60 grain .22LR stabilizes just fine out of an AR-15 barrel (most .22LR firearms won't stabilize it properly and you get keyholing). It's more expensive than regular .22, but it works just fine. The shorter cases do have a tendency to get stuck in the action but they are easy enough to dig out. Just keep the conversion kit lubed nicely. I use this SSS out of an AR I built for the purpose- with a suppressor it's extremely quiet.