Actually it sounds a lot like the 276 Pederson that was being experimented with before World War Two. Gerneral Hatcher said the terminal effects of a FMJ bullet from that one were lackluster.
The reason he said that was they wanted to use up the left over10 bazillion WW I 30/06 cartridges rather than start a new run of a new cartridge.My Uncle was working at The Armory and was testing the M1 with the 276 and thought it was an excellent cartridge.He used it at Camp Perry to win a chit load of matches.
General Hatcher did write in his book about the subject that he did like a 256 experimental cartridge they were looking at during the same time. He actually favored the 256 and said it's terminal effects were very good.
He hunted with a 257 Roberts based on his experience with the experimental 256.
