P14 gunsmithing needed for a 444 marlin

I know some of the learned members here have done a range of rimmed conversions on ex-mil actions. I was considering getting a 444marlin done on a P14 I have. I know SMLE and others would be easier, but Im chasing the high action strength advantages of the P14. Im not a gunsmith myself so would get one to do the work. Main question is how much work is involved? If its a reasonably easy conversion I will engage one, but if its going to be 30-40 hours work I wont bother pursuing. Thanks if answers could be around the 444 marlin, not a 45-70, I have a lot of 429 projectiles I intend to use. Also if another exmil action is similar strength and lends itself better to the 444, please suggest

A quick test- remove the striker from the bolt.
Try to load a .444 round into the magazine. If it stays in place- good. Now push the bolt forward and see if the rim starts to slide up under the extractor before the cartridge is stopped by the .303 chamber.
It’ll be a lot of work if it fails these tests.


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The .303 British cartridge has a larger diameter rim than the .444. The difference is nearly 30 thousandths. If the extractor will work for the smaller rim will the ejector as well? If they need to be built up it will add hours to the smithing.

Jim

Over in Pakistan,
They converted the British P14s to sniper rifles that fired a 7.62x 54r Russian round by making the barrels out of surplus Russian machine gun barrels.
The barrels were long and chrome lined so they were very accurate.

30 to 40 hours of work is not a reasonable expectation of what it will take to make this conversion. Besides the bolt face being too large in diameter, the bolts are quite hard so I would recommend TiN, TiCN, or TiAIN carbide tooling for machining on hard steel. The extractor claw would probably be too short for proper rim engagement, so you might need to build up some material with your TIG welder and re-contour the claw. The magazine, follower and feed rails were designed to function with a rimmed bottlenecked cartridge, and the 444 is a straight walled cartridge. You might need to modify the feed rails, feed ramp, and follower in order to get the cartridges to feed.

You'll need to machine a new barrel from a 44 caliber blank. The P14 uses square threads on it's breech, and has a flat breech face. On this breech face is a semi-circular cut for the left bolt lug that is .045" deep. To make this cut, probably the easiest way would be to set up the barrel in your indexing head on your Bridgeport mill, then use your right angle attachment on the mill to make the cut. There are probably other ways to make this relief cut, but the one described is probably the easiest for a gunsmith to do. Making a Pattern 1914 into a 444 Marlin is doable, and is probably equal in difficulty to making a 45-70, but the expectation that it can be done in a week or two is not realistic.

There are two options off the top of my head that would be much easier. First, Criterion barrels is going to be releasing new P14 barrels in 303 British soon. They're already taking orders. This would be as close to "plug and play" as you could get. Second option: A P14 action can work when converted to 30-40 Krag, with making and installing a barrel in that caliber as the only modification. Rifles in everything from 30-30 Winchester to 505 Gibbs have been built on P14 actions, but working with this action requires serious gunsmithing skills.

Another option for a possible 444 bolt action conversion would be to use a Savage 110 magnum action. Most belted magnum cartridges use the same case head diameter as the rim diameter of the 303 British. Because they use a sliding plate extractor, they would be more forgiving on rim diameter than a claw extractor. It's counter-intuitive to use a magnum action for a rimmed cartridge like the 444, 7.62x54, 303, & 30-40, but the bolt face diameter is similar.

Update: I was out in the shop filing the tool marks out of a barrel that I was contouring, and I had plenty of time to think about things. If you want a Milsurp action that can be made to shoot rimmed cartridges like a 444 Marlin, has reliable single stack feeding, can be built "relatively" inexpensively with modifications like widening the magazine well and a re-barrel, then a Mosin Nagant might be a good choice.