[tikka250]

i dont see much wrong with how you are doing it. i find shooting a 22 offhand does wonders for my centerfire rifle shooting. i am fortunate enough to have some good gopher spots so thats where most of my rimfire shooting is but any type of varied distance shooting spots work fine. i used to spend hours at an old gravel pit shooting small rocks or dirt clods on the bank.
as for shooting targets offhand at 300 and beyond i say dont hold yourself back the best way to learn is to push yourself.