I have a friend with his grandfather's gun. It is a M70 Winchester from the 40's. 257 Roberts is x'd out and 250 HD is stamped next to it. Anyone know what this could be?

Perry

not listed in P.O.'s books that i could find.

Ha! It's posted above. The Krag improved

I had a few chamberings jobs in the early 70s , it was the 250 hell driver or hell diver .
I still have some boxes of formed ww2 30-06 brass somewhere in the shop .

There is a 250 Humdinger (HD?) although probably a much later wildcat than the era of your friends rifle.

Well...interesting story.
I assumed it was the Hell Diver, that is a Wallack and Holmes wildcat and they are the one's who did the barrel. Right time period for it too.
I pulled the gun out last wk and started taking measurements and low and behold it is a 257 Ackley Improved. The above forementioned is based off a parent case of the 30-40 Krag which is a .545 dia rimmed case. The chamber on the rifle is a standard .473 bolt face, non-rimmed. I found a couple other stories deep in the internet of folks having barrels stamped 250 HD's that turned out to be improved 257's also. So at some point W&H's were stamping their bbls 250 HD's when they were not the true 250 HD's. I find that thinking odd, maybe they did'nt own a "7" stamp .
I have to say I am somewhat delighted as I have lots of 257 brass and there is plenty of load data out there. Not to mention re-barrelling options are endless should I shoot this on out.
Ray Atkinson gets the wisdom award on this one. First post in on another thread about this chamber he suggested a cast, then later in the post again suggested a cast. listen to your elders!

Perry