Another forum I hang out on had this gun come up. 1941 rifle, sure appears all original and is marked 300 Magnum. Is it a 300 H&H?

http://hunting-washington.com/.../topic,198934.0.html

In 1941 I am pretty sure the only commonly available 300 magnum was the 300 H&H. It is not unusual for a M70 of that vintage to be marked "300 Magnum".

The 300 Winchester Magnum was not introduced until 1963,so not surprising it would not chamber in the H&H rifle.The cases are much different.

Of course in checking any pre 64 M70 300 H&H fromm that era, it's always wise to be sure the rifle was not rechamsbered for 300 Weatherby, which was a common fate for pre 64 M70 300 H&H's.A 300 H&H case will easily chamber in a rifle chambered for the 300 Weatherby.

300 Win Mag rifles were only made at the very end of the pre 64 Model 70 Winchesters. It is almost 100% that the rifle in question is a 300 H&H Magnum.

Eastcoaster is correct. It's a 300 H&H Magnum...

And the owner cannot get a .300 Win to battery, ie., chamber has not been opened to .300 Roy.

I have an old box of Remington 300 magnum brass and they are 300H&H brass.

Ive owned a number of pre war and pre 64 Win. in 300 H&H mag. as well as some Rem. mod. 721..All were marked 300 H&H Mag....

Not saying none were marked 300 mag. but just that none of mine were..

I might be inclined however to take a chamber cast, and that's not expensive..

Those with Rule's book can turn to page 115 for a picture of an early M70 barrel marked "300 Magnum".

Not unusual.

My hunting partner has a Winchester Pre-64 that is marked 300 magnum on barrel. It is a 300 H&H.

Ditto, pre-war or early postwar M70s marked 300 Magnum were chambered for 300 H&H from the factory.

yep H&H, and pretty collectable.
even a rough one will bring over a grand easy.
I have been chasing a decent one to use for an ELK rifle for years now.