RE: What next to improve my groups?
UMC is good for plinking and plenty cheap, but not so accurate. With a new scope, you could use it to get you in the ring and then switch over to your hunting loads. I have had really good luck with silver bear, and it's almost as cheap. I get 2-2.5" groups from the silver bear 223 shooting it out of an AK sporter carbine. Killed a 6 point with it in Nov. and was impressed with the expansion of the HP.