Since the .22-250 is one of the smaller cases that uses a large rifle primer, I generally use one of the "colder" primers - like the Remington 9 1//2. In terms of powders, H-380, IMR4064,and WW760 are three of my favorites. The rest you should probably get from a loading manual. Also, the new Sierra 55 gr. Blitzking bullets have shot particularly well in several .22-250's of mine - might be worth a try. Expansion on varmints is great!