According to my research, serial number 129149 puts date of manufacture at 1948 and began life as a 30-06. Belonged to an uncle of the former owner and saw most of its life hunting in Africa. Previous owner had the bolt face and feed rails opened up to magnum.

I've been looking for a suitable Mauser action for a medium bore build for about a year, so when this popped up for $500 NZ I jumped at the chance.

Initially, I looked at a 9.3x64 build however brass is expensive and not readily available here in New Zealand, though projectiles are..

However, .375 Ruger is a different proposition because factory ammo is available here as well as brass and projectiles.

From what I understand these actions are not really suitable for conversion to H&H length.

Can certainly be opened up for H&H size cases....

Cheers,
Mark.

Maybe not suitable cost wise but ALL pre-64's were the same length, Hornet to 375

I used the exact same action to build my .375 Ruger. Just needed to open the boltface to accommodate the Ruger but functions great and shoots even better! Kevin Weaver of Peyton, Colorado built mine.

It will work very nicely.

True that all the Pre-'64 actions are actually .30-06-length, same as a standard M98.
So they had to be opened expertly at the factory when made into .375 H&H.

The Post-'64 actions, pushfeeds and Classics etc., started using a .375 H&H length
that had to be blocked at the back of the magazine to fit .30-06 length.
Of course there are the shorter-than-standard-length M70 actions too, like for the WSM's etc.

Above is my action similar to yours, mine made in 1950, SN: 160XXX. It was first a .30-06, then a 300 Win. Mag., now it is a .458 Win. Mag.
The barrel is from a CZ .458 Win. Mag., set back only 1/8".
The major diameter of the M70 barrel threads fit inside the minor diameter of the CZ barrel threads.
I call this the WinCzechster, and I would not change a thing about it.

Reinforce the front of the sheetmetal magazine box if it has not been done.
Prevents dimpling the front of the box from bullet-nose battering in recoil.
If the front of the box is not smooth it might hesitate in feeding.

Rip ...

As noted, the external dimenstions of Pre-64 70s are the same; the difference being the magazine is opened 1/8" in front and 1/16" in back. Removing such metal is best not done if other options are available, and in this case, it's best not done. there are several "standard" length magnum cartridges to get the performance of the 375 H&H.
I rather like the recent trend in cartridges initially based on the 404 where the base is magnum diameter (.532") and the sides are straight with no belt. Congratulations on your great find and best wishes for a completed project with which you will be very pleased.

A pre 64 Win is suitable for sure, and 48 was a good year, nicely finished at the factory back then..I will make into a very nice 375 H&H or Ruger.