Any rimfire can play - Check, organize by caliber, sure that's fair, match .22 LRs will dominate otherwise.
Target - I still think 4 groups versus 5. Think of what you get out of a box of ammo (50 rounds). Shooting 4 groups allows you to make two attempts with allowance for 10 sighter shots. 5 groups, two attempts, no allowance for sighters, bring another box of ammo. With .17 HMR floating around $20/box, same with match grade .22 LR (not sure about .22 Mag prices, don't own one), conserving some ammo while shooting this appeals to me. Use whatever target you prefer, so long as it is clean of any non-attempt shots, aside from sighters shot at designated sighter bulls.
If you want the average for the .22 Mag at 1.5" that's cool, I don't know what to expect from them accuracy wise. For the .22 LRs, that's just too easy, it's supposed to be a challenge, right? Same with .17 HMR, I still say keep these two under 1" average, and that is plenty attainable while still being challenging. By using an average, you have allowance for one group going sideways, which will happen often at 100 yards.
Target - I still think 4 groups versus 5. Think of what you get out of a box of ammo (50 rounds). Shooting 4 groups allows you to make two attempts with allowance for 10 sighter shots. 5 groups, two attempts, no allowance for sighters, bring another box of ammo. With .17 HMR floating around $20/box, same with match grade .22 LR (not sure about .22 Mag prices, don't own one), conserving some ammo while shooting this appeals to me. Use whatever target you prefer, so long as it is clean of any non-attempt shots, aside from sighters shot at designated sighter bulls.
If you want the average for the .22 Mag at 1.5" that's cool, I don't know what to expect from them accuracy wise. For the .22 LRs, that's just too easy, it's supposed to be a challenge, right? Same with .17 HMR, I still say keep these two under 1" average, and that is plenty attainable while still being challenging. By using an average, you have allowance for one group going sideways, which will happen often at 100 yards.