CIG- Neck sizing only will increase your brass life, but may make for more difficult chambering - not good if the rifle is going to be used for dangerous game, but not really and issue for practice / bench loads. For hunting loads, in a heavy recoiling cartridge like a .375 H&H, I would crimp to minimize the chance of bullet movement in the magazine from recoil; again, not an issue with bench / practice loads. Each rifle is a law un to its self when it comes to handloads. I have found that seating close to the lands generally results in an accuracy improvement, and that a tight neck / bullet fit is generally preferable to trying to crimp outside of the bullets crimping grove. The best way to determine what shoots well in your rifle is to experiment with bullet seating depth, bullet make and weight, primer and powder selection, crimping, etc. From what I have seen, bullet weight and velocity seem to have the biggest single effect in the accuracy of a load in a particular rifle, with other changes more like fine tuning (But not always..) Any quality .375 should do better then 4 inches at 100 yards. Recoil should also be considered - its a lot easier to get good groups with a .223 then a .375... Reduced velocity practice loads make a heavy recoiling rifle a lot more fun.
Larry
