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A Mosin in 500 SW

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A Mosin in 500 SW

Postby Shepard » Wed Feb 22, 2012 6:16 am

I've been working on an idea for a 50 caliber Mosin. Ever sense M1 found McGowan barrel company my heads been spinning like a top with crazy ideas on building guns based on old Mosin receivers. Here's the goo -- 500 SW is a rimmed cartridge with a base size .010 smaller than 7.62x54R, so the extractor should pull the case with no problem. McGowan cuts the receiver thread and short chambers it. All you gotta do is ream it setting the proper head space and wa-la you have a single shot Nifty Fifty.
Now the other day someone posted a pic of a Jap single shot training magazine and the idea of a magazine adapter came flooding in to my brain. Does anyone make a slide action 500 SW? I need a mag that supports the big cartridge with 5 to 9 rounds. There's a company that makes a conversion kit to fire 45 ACP's out of an 303 Enfield and it uses standard 1911 mags, so why not a 50 caliber?

http://www.specialinterestarms.com
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Re: A Mosin in 500 SW

Postby DevilDog » Wed Feb 22, 2012 10:08 am

Shep, thats really out there..but I like it. Have you popped a 500SW cartridge into a boltface? Does it hold?

Lots of stopping power, accuracy out to 200yds I imagine.
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Re: A Mosin in 500 SW

Postby Marauder 1 » Wed Feb 22, 2012 10:30 am

Sounds kind of interesting.. I was looking up case pressures for the 500 here is the link
SW 500 Data
450px-500SWMag005.png

The .500 S&W Magnum has a maximum working pressure of 60,000 psi (4,100 bar). However, most factory ammunition is limited to 50,000 psi (3,400 bar) to help ease extraction of fired cases. The cylinders of the S&W Model 500 revolver are engineered to be capable of withstanding 50% over pressure. Regular proof-load testing is performed at 20% over pressure.[6]

Cylinder bore ∅ is given as .500 in (12.7 mm). SAAMI recommends a 6 groove barrel with each groove being .130 in (3.3 mm) wide. A barrel with a bore ∅ of .4880 in (12.40 mm) and a groove ∅ of .4983 in (12.66 mm) is also recommended. The recommended twist rate is 1 in 18.75 in (476 mm). While the bore diameter of .4880 in (12.40 mm) is consistent with other firearms which fire a .500 in (12.7 mm) diameter bullet, the groove diameter of .4983 in (12.66 mm) is an oddity as most firearms which fire a .500 in (12.7 mm) will have a groove diameter of equal to the diameter of the bullet.[8] For this reason regular cast lead bullets should not be fired in the revolver as excessive leading of the forcing cone and barrel will occur, leading to excessive pressures or the deposited lead acting as an obstruction in the barrel or forcing cone.

While the overall length is given as 2.300 inches (58.4 mm) by many sources, some revolvers will not be able to accept cartridges with bullets seated to this overall length. This is because the cylinders of the revolvers are too short to accommodate such cartridges. The now-discontinued Taurus Raging Bull 500 is an example of one such revolver. It has a cylinder which is about .200 inches (5.1 mm) shorter than that of the S&W Model 500

7.62×54mmR maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm).
400px-7.62_x_54_R_cartridge.svg.png

Americans would define the shoulder angle at alpha/2 ≈ 18.5 degrees. The common rifling twist rate for this cartridge is 240 mm (1 in 9.45 in), 4 grooves, Ø lands = 7.62 mm (0.300 in), Ø grooves = 7.92 mm (0.312 in), land width = 3.81 mm and the primer type is Berdan or very rarely Boxer (in large rifle size).

According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) guidelines the 7.62×54mmR case can handle up to 390 MPa (56,564 psi) piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers.

If you went to 60,000 psi I think the lugs should be able to handle the difference in pressure.
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Re: A Mosin in 500 SW

Postby Shepard » Wed Feb 22, 2012 10:55 am

Thanks for sharing. The info on the 500 SW is the same tech info I used for my idea. I figured by looking at the numbers real quick that the receiver would be able handle the pressure leaves. At this time It's only an idea. In reality I'm saving some cash in hopes to start this project sometime in the next 6-8 months. I'm looking for feedback and any help that may be offered.
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Re: A Mosin in 500 SW

Postby Chenko » Wed Feb 22, 2012 11:10 am

i dont really understand what this all means but it sounds pretty neat. would this be possible with .338 lapua?
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Re: A Mosin in 500 SW

Postby Shepard » Tue Jan 07, 2014 9:47 pm

Well it took some time -- but its coming to pass. The Nifty Fifty is going to be a reality 2 times over. I have 2 50cal barrels headed to my shop as I write. I'm planning on renting a reamer for 4D rentals to do the chambering. A 50 caliber pistol bullet loaded for a rifle out of a 25" barrel will be traveling like a freight train on fire. I can't wait to run these through my graph to see what kind of speed they'll travel at. I've decided that I'm going to do a metal stock in the straight line form. I'll use all the goodies that we've used before. Now that I've looked over the load data I'm thinking this will actually be a much longer range rifle then I originally thought.

Timney trigger
RSI original mount
Weaver 6 screw rings
SWFA10x42 SS scope
1.200x25" Green Mountain barrel 50 caliber 1 in 19" rate of twist
Limb Saver recoil pad
Brake from Muzzle Brakes and More
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A Mosin in 500 SW

Postby Gamecock24 » Wed Jan 08, 2014 8:04 am

Jerry so you're going with a muzzle brake yours. I was considering that but wasn't sure if I wan to the extra length on the barrel. I know how the recoil of 500SW is out my hand gun and hits hard but I'm hoping the weight of the rifle will help with that. I am going to get a recoil pad though. Sounds like yours is going to be a lot different than mine so I can't wait to see what you do with yours.

You may find this useful if you haven't seen it yet. Some ballistics from H&R handy rifle in 500SW.
Image
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Re: A Mosin in 500 SW

Postby Shepard » Fri Jan 10, 2014 1:07 am

Well I received a package today from Green Mountain -- 2 beautiful 50 caliber barrels all nice and shinning. These are finished to a standard 1.200 diameter with a nice high speed finish. I unpacked them and checked the barrels over to find there 27 inches long not 25. This is going to be one strange shooting rifle. Aren't Mosins grand!!!!!!!!!!!!!!!!!
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Re: A Mosin in 500 SW

Postby Marauder 1 » Fri Jan 10, 2014 1:24 am

Don't you just love it when you get a package like that!!

So Shep I have a couple questions, what do you expect the muzzle velocity will be? Will you have to use a slower powder to keep the pressures under control?

Sounds like an awesome project I look forward to the results. I've often thought about a .45LC Mosin but that would require to much in the way of modding the magazine to get it to work.

Keep us posted please.

Mark
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Re: A Mosin in 500 SW

Postby Gamecock24 » Fri Jan 10, 2014 5:31 am

Wow. That's unexpected 27" not 25" I do wonder how they are going to compare to the handi rifle with 22" barrel.
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