I have the standard sporter RAR in 17HMR. the only ammo I have tired in it is the Hornady 17 gr., it groups consistent 5 shot sub-1/2" groups at 50 yards and consistent 5-shot 3/4 to 1 inch groups at 100 yards. I do not see any point in trying any other ammo.
I was reluctant to try the RAR 17HMR because of a poor shooting RAR 22 LR I had, but I got such a good buy on the 17HMR that I couldn't pass it up. Now that I have it I am really happy with it, it has become my favorite ground squirrel rifle. Hope yours is a good one.
drover