I have a set of .338-378 weatherby magnum RCBS full length, trim and case forming dies. I also have a shilen barrel for a ruger #1 in same caliber. What in the hell can a guy do with those things? I had thought they were from a weatherby rifle until I actually got them home.

Well for starters the Ruger barrel thread 1"x16 tpi is the same as the M70 winchester. Food for thought.

Is the barrel already chambered too?

Yes it is chambered for the 338-378 weatherby magnum. Does winchester make a M70 action in a length suitable for that round?

I can't say if its possible or not. I've never heard of one of the big Weatherby cartridges on that action but I am certainly not the end of all knowledge. If there is enough shank you can cut the threads off and start over or you can suck it up and get a #1. Unless you really really want a #1 in that caliber I would put the stuff on eBay and try to get out whole.

I think there is enough shank left of the barrel to cut it off and rechamber to a 338 win mag but I'm not sure of that. I doubt I can re-use the barrel for that huge weatherby case. Seems to me the barrel should work for something.

I am in the same boat with a beatiful integral rib barrel roughed out for 416 Rigby. The threads were turned off and I have one of two choices, bush the threads and use as-is which will require some serious analysis or cut the threads off and live with a rather unusual barrel profile. I haven't been able or willing to decide yet.

I am also not sure how much chamber you will have to surrender to get to a 338 Win Mag. You can overlay chamber dimensions to find what your options are.

Why not put the barrel on a #1 Ruger Tropical?

It sounds to me like you're "hosed"

Ja! Yust put it on a No.1 action, unt be happy!!