just to throw my 2 cents in here. to the op are you shooting competitions or just plinking? true the big cartridges are hard on barrels. i have shoot a 280ai (comparable to 7mm saum) for several years now. it is supposed to be done at around the 1200-1400 round mark, the last one i pulled off had over 1600 rounds through it and was still shooting in the 1/2 moa range at distance. i pulled it because it was copper fouling more than i cared to clean. that barrel used 162 a max at 3000 fps. my current 280 barrel has 1000 rounds through it (180 berger at 3000) and is shooting well under 1/2 moa at 1000 yet. the throat is definetly firecracked so i expect it will start fouling like the previous barrel, but is good as of this point in time. so far as shooting out to 1 mile, you don,t need a big cartridge to get that done. i have a 284 that i shoot the 162 a max at just under 3000, and have shot it to 1 mile numerous times now. the biggest thing with the smaller calibers is spotting your mises at that distance, so you need a dirt type target backing. the 284 is much easier on barrels than a lot of the bigger cartrides as well. my shooting partner has a sister rifle to my 284 and he has over 1600 rounds through it and it cleans up nice and easy,... and when we shoot at 1000 he gets vertical in the order of 3". if this is your first build i would go with the 284, long barrel life so you can shoot lots and enjoy.