What do you think of the "Ultra" mag? My Self, as a custom rifle builder I am not impressed by it. It beats out the 300 Weatherby by a few feet per second with a hell of a lot more recoil. I have not seen any extreme accuracy with factory rifles. To really capitalize on this cartridge and its 7mm brother you seem to need a slower twist and 29" barrels. For example I built three 7mm ultras before Remington came out with it and to get what we should get for performance and accuracy we ran 1 in 11 twist barrels and 29" for length. With a standard 1 in 9 twist we found that 140 grain bullets would shoot well until we exceeded 3400 fps then the groups opened up. With the 1 in 11 twist we reached 3570 fps with three shot groups averaging .427 extreme spread. Now the 1 in 9 twist of a rechambered Sendaro, after some "tweaking" shot 175 grain bullets into one hole groups at 3450 fps.
Both these cartridges do not really seem to go well into a practical, easy handling hunting rifle. However if one wants the ultimate .30 cal look at the 30/378 and forget the Ultra but again you want a 29"+ barrel and heavy bullets, 165 or heaver.
