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Old August 21, 2015, 05:32 PM   #1
dakota.potts
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Pedersen-like device for Mosin Nagant. Am I crazy?

I was doing a little bit of reading on the Pedersen device yesterday and I started thinking. For those who don't know, the Pedersen is a device invented to turn bolt action rifles into semi-automatic rifles firing a pistol caliber round.

It seems that, in experimenting with chamber inserts, people were finding the .32 ACP pistol round to work better than other options like the 7.62 Tokarev, because the .32 fits the bore of the Mosin Nagant better than other pistol rounds.

It got me thinking, could you fashion a drop-in device that allowed you to fire .32 ACP rounds from the Mosin Nagant without manually cycling?

My thoughts are maybe using the parts from another firearm available on the market (like the Vz. 61 Scorpion). The scorpion is a blow-back operated .32 ACP submachine gun/pistol that feeds from 20 round magazines. This would allow you to use magazines that are already available on the market.

It seems like you could use the existing hammer and sear, and maybe even use the disconnector from the Vz. 61 parts. I imagine you would need a disconnector to keep from making a machine gun.

My thinking is you could machine a receiver that would hold the bolt carrier group, ejector, magwell, and extractor pieces. Utilize the right side bolt cutout on the receiver as the position for the magazine, and maybe you could tinker with ejection to make spent cases eject out of the top? In this way, you could avoid having to cut the receiver for extraction and keep the Mosin in its original condition. If necessary, you could also utilize a .32 ACP chamber insert instead of machining that into the device.

Am I wrong in thinking that is is not only possible, but not incredibly complicated? Treating the whole assembly like a pistol minus some of the more complicated parts (barrel, chamber, fire control group, etc.) it seems like you would only need a relatively small number of parts for a simple blowback system. You could cut down even further by sacrificing a bolt hold mechanism in favor of a simple system like that of the AK.

I have CAD and some minor skills that I may play around with to try to plot something out, but I'm not even sure where I would start on something like this.

As for why, really just for mechanical curiosity
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Old August 21, 2015, 07:45 PM   #2
Catfish
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The reason for the Pedersen device was for close range trench warfare, more fire power at close range. I guess that your reason would be just because you can. You would need to rebarrel or rechamber for the round and modify the rifle to take a magazine to hold the 32 ammo. Next you need to make a semi-auto action that will slide into the action. Sure it can be done, but sure looks like a lot of work for something that has no use.
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Old August 21, 2015, 07:53 PM   #3
Jim Watson
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They actually prototyped Pedersen Devices for MN and 1917 US Enfield.

Could I reproduce it? No.
Can you? I don't know.
Can you afford to have someone else do it? Crazy money.
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Old August 21, 2015, 08:08 PM   #4
Bill DeShivs
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And, you would still have a huge old gun that shoots a tiny pistol round.
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Old August 21, 2015, 08:08 PM   #5
dakota.potts
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My reason would 100% be because I can. I'm a student of machine technology and gunsmithing (although I've only done my general education class up to this point and I start my machine tool classes on Monday) and I'm just trying to look at things in a different way.

There are chamber inserts available that allow the rifle to be chambered for .32 ACP. It's shaped like a 54R cartridge and slides right in.

The Pedersen device was also designed to hold a magazine itself off to the side of the rifle, not modifying the rifle itself.

It's coming up with the semi-auto action to slide into the rifle that I'm most curious about.
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Old August 21, 2015, 10:31 PM   #6
Jim Watson
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Quote:
The Pedersen device was also designed to hold a magazine itself off to the side of the rifle, not modifying the rifle itself.
I don't know about the other rifles they made prototypes for, like the MN, but the 1903 Mk I had an ejection port on the left receiver rail and had a special bolt stop and sear to retain and fire the Device. Most of the bolt stops and sears were replaced with standard when they dropped the project and scrapped the devices, but no way to close the extra ejection port.
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Old August 21, 2015, 11:04 PM   #7
dakota.potts
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Right, what I meant was that the original magazine well of the rifle was not modified.
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