any ammo that you will pay more than $6 US for a box should be uniform in velocity, if you want to get to Masters (considering what you wrote on the bottom) then I would suggest finding ammo that shoots 1 inch -1 1/4 at the rams. I think that cronograph your 22 is waste of time, sugestions for a good ammo would be LApua MAster, eley (at least ) black box, some better RWS like "rifle target". I shoot Lapua Master, and at one time i was sorting it by rim thickness and I shot 5/8 group at 100 (11 shots), unfortunatelly It got late and I could not test any more than that, but I got so hooked on that group that I certainly will repeat my testing next year.
all 22 match ammo will shoot around 1080 fps, and I heard others opinion
that rim thickness sorting will improve accuracy, but I still have to do much more testing before I will be convinced, I remember we tested some old Fed GMM 900, couple years ago, and this stuff was so even that it was a waste of time,
all the best
shootingpaul