I am having a custom tactical rifle built from nighthawk tactical. I'm really having a hard time deciding on the caliber to go with. I know the 300 mag is a very accurate round and may be the caliber i go with but i'm not set on it yet. I'm also thinking of the 300 RUM and the 338 RUM. I already have a 375 RUM in a 700 Rem XCR that i load with 260 gr accubonds and 96 gr of IMR 4350 and i would like to think that with that load and the MK IV 8.5x25x50 leupold that i could take big game at 1000 yds. However, i think that with that big of a round my accuracy may have went down. Any and all help i can get i'd sure appreciate it.