My browning groups around 1-1.5 inches at 100 yds and the kimber is at 1.5-2inches+ (so far a very disappointing rifle).

I understand I can not get a definitive answer, I was just hoping for suggestions as to a good starting point to begin looking/experimenting.

Cabelas alone has over 30 different types of 308 ammo and 20+ types of 300 win mag. If I buy one box of each to experiment at let's say $40, I am looking at a cost of over $2000. I am probably naive, but is everyone really spending over a $1000 per rifle to find the best ammo? Or with some good suggestions, can that field be dramatically narrowed? Thanks again for your help!