.450 Mosin Nagant?

I know of one so far, let's see if more show up.

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.450 Mosin Nagant?

Postby Navy_Guns » Wed Jul 20, 2016 9:20 am

Years ago I bought a Mosin Nagant M44 with a sewer pipe barrel for $50 as a project rifle. I had wanted to rebarrel in .454 Casull since I have a revolver for that cartridge, it is a rimmed case, and it appeared that with some modification I could push-feed cartridges right out of the magazine. I got as far as acquiring a Douglas .452" barrel and a .454 Casull reamer. Eventually I got my 20" .450 Bushmaster upper and now I'm rethinking the .454 Casull in favor of a bolt action Bushmaster.

The case head diameter is smaller so I would have to deepen the cut for the extractor on the bolt head and maybe get a longer extractor spring. On the plus side, it would be much easier to rebarrel because I wouldn't have to index an extractor cut on the barrel stub. So long as the chamber fully supports the side wall of the cartridge, I could have a nice clearance gap between the end of the barrel stub and the bolt face. I may not even have to do anything about the clearance between the 450 Bushmaster case head and the lip on the bolt face. I believe that lip is just there to help keep the tapered cartridge case engaged to the extractor until the case is fully extracted and reaches the ejector. If extraction was a problem, adding a "C" shaped shim ring to the bolt face shouldn't be too hard. Some mods may be required for the existing ejector to work with the smaller case head. Use of the magazine may be possible with modification.

So if I have a .450 Bushmaster upper, why go to the trouble? Because I have the barrel blank and the action already, and it would be nice to have something I could use for heavy cast projectiles without fears of bunging up my gas system. Opinions welcome.
762x54r vs 450 Bushmaster.png
7.62x54r at max CIP dimensions, 450 Bushmaster at max SAAMI dimensions
762x54r vs 450 Bushmaster.png (78.47 KiB) Viewed 1711 times
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Re: .450 Mosin Nagant?

Postby Texas Sheepdawg » Sat Jul 23, 2016 7:35 am

Ummm. Do you think the Nagant action can handle the SAAMI pressures of a 450 Bushmaster?
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Re: .450 Mosin Nagant?

Postby mikluck » Fri Jul 29, 2016 3:45 pm

New here but i bought my fist upper yesterday, Bartz 20" (nearly the same one Hoot reviewed a while back). But I love the old Mosin Nagant and this piqued my interest...

Ummm. Do you think the Nagant action can handle the SAAMI pressures of a 450 Bushmaster?

450bm SAAMI Pressure is 38,000 PSI. I'm sure that's well stated a few times here on the forums.
From what I can find it seems the 7.62x54R max pressure is 56,000 PSI. Europe's CIP would be the source of information and regulations on the 7.62x54, however I didn't have any luck going through their website.

I'd really like to see this project progress as I have a Mosin I've been trying to figure out what to do with.

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Re: .450 Mosin Nagant?

Postby pitted bore » Sat Aug 06, 2016 10:12 pm

The subject of 450 bushmaster and the Mosin-Nagant rifle was brought up about four and a half years ago in this bolt-action forum.

I did some calculations, and produced a very rough prototype of a 452 cartridge based on a sawed-off 7.62x54R case, and wrote some posts.

In the posts I linked to a number of web pages to show my sources. Most of the links are still active, except the one to the Russian site. (It pictured a splendid Montengrin revolver chambered in the 11.3 Montenegrin cartridge.)

Link: Had an idea for a 45 or 458 caliber Mosin Nagant.

As you indicated in your post, the extractor problem is central to a good conversion. I've not tried to play with a cartridge having a rim and body smaller than the 7.62x54R. I did have a bolt face opened and the extractor modified to take a 348 Winchester-based wildcat. The 348 Win case is conisderably larger in rim and base diameters than the 7.62x54R case. However, that project ended before any shots were fired, and the rifle went down the road.

Please keep us posted on your thoughts and work.. It's almost certain that I cannot pursue this further.
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