I think it was a 30-06 Featherweight based on barrel contour and length. It also appears to possibly
have a recoil pad of some make-unless my eyes are tricking me. I have an 06 Featherweight and it looks identical.
Many bear and moose have been shot very dead with the 30-06 in Alaska. It still remains popular
along with the 270. Featherweights originated in the 1950s, Super Grades but no magnum calibers AFAIK.
It's a factory aluminum butt plate. Low comb stock. Second picture clearly shows it as a FWT barrel contour. No way to guess the barrel length in the picture. But assume it is a factory 22" with factory front sight. The only fwt it could be would me made from 1952-1957. In 1952-1954, the only fwt available was the 308 winchester. Like I said, the rifle appears to have been used for a couple years. This is noted by the missing front sight hood. Although, some guys removed them before a hunt. Most guys I know left them on, until brush or the like ripped them off. BTDT. In 1955 winchester brought out the 243, 270, 30-06, 358win, fwt's.
As for "magnums": Of course there were magnums back then. 375H&H, 300H&H, and 458wm to name a few. However, that is clearly a fwt barrel contour. Hence not any kind of magnum. The 264 win mag came out in 1962. The 338wm in 1959. The 300wm was introduced the last year of the pre 64. The only one of those magnums that had the fwt barrel contour was the 264, but came out much later than the picture from 1957.
If I could see the bolt ovid better, that would tell me if the rifle was made before 1954 and narrow down the cartridge it housed. Solid and it would be a 308 Winchester, made in 1952 or 1953.
Not many people would have messed with an original rifle like that, but just used it. That's why I believe it is all factory, as it also appears that way in the 2 pictures.
There were also guys handloading their own ammo back then. AK brought up the 358 winchester. That was rare, even back then. So my guess is not. Even though the 358 would be a dandy Alaskan cartridge. It's more than likely a 30-06.