M1 Carbine ->Tokarev?

[bkbville]

I've been kicking around the idea of converting a plainfield M1 Carbine to 7.62x25 Tokarev.

Honestly I don't have much experience doing this, but the approach I was hoping to take was to preserve the existing barrel/gas system and rechamber it; the bolt face would need to be opened up a bit (about .030"), and I think the carbine mag would work.

Now, the 30 carbine case length is amost .3" longer than the tokarev. If I'm using the existing barrel and reaming the new chamber, what would I need to do with that extra .3" beyond the end of the tokarev case?

Can it be left? Is there some sort of sleeve that can be used?

 

[TehK1w1]

chop .3" off the breech end of the barrel and screw it in further, maybe? That would seem to be the simplest solution.
I am not a gunsmith, so listen to my suggestions at your peril

 

[U.S.SFC_RET]

I don't know if this has ever been done before.

The chamber cannot be shortened. If you do then the gas piston will be moved rearward. If the piston moves rearward then it will never fit when you assemble the slide. Unless you mill .3 off the back of the slide.

If you modify a .30 cal carbine bolt remember that headspace consists the front as well as the back of the locking lugs.
If in the event you do modify then you might run into dangerous unchartered territory.

You will also have to modify the bolt face. To include the extractor. Which I would never attempt.

If you are successful in receiving a customized bolt, slide and barrel I would like to hear about it.

Good luck.

 

[rcmodel]

What is the goal?

To shoot cheap surplus corrosive ammo, with less performance then the .30 Carbine round has to start with?

The other thing is, the .30 carbine has a .308" bore and the 7.62x25 Tokarev has .310" bullets.

It is also unknown if the pressure curve of the powders used would operate the gas system properly on the M-1 Carbine.

rc

 

[dirtyjim]

there was a guy on another forum that converted on to 7.62x25 & 357 sig. a couple of years ago. i don't remember what forum & the pictures i saved of it were lost when my previous computer had a meltdow. if i remember right he started off with a wore out barrel. he cut the barrel off right in front of the gas piston then reamed & threaded the old section of barrel with the gas piston & receiver threads. he then turned a barrel blank to thread into the old section & drilled a new port for the piston. chambered the barrel & modified the boltface & extractor.
it can be done but it would be a lot of work.

smith & weson converted one to 40s&w too, it was actioned off by kull & supica a couple of years ago

 

[Clark]

I have modified some long guns to use up 7.62x25mm Tokarev ammo.

The 86 gr surplus ammo is not very accurate.
The S&B ammo is ok.

 

[Sunray]

"...using the existing barrel and reaming the new chamber..." Nope. New, cu$tom made, barrel. Different bullet diameter(7.62 doesn't always mean .308". .308" doesn't mathematically convert to 7.62mm either.), bottle necked case vs straight(tapered).
The carbine case is 306 thou longer than the Tokarev case and 303 thou longer OAL with the bullet.
"...headspace consists the front as well as the back of the locking lugs..." Headspace has nothing whatever to do with the locking lugs.

 

[U.S.SFC_RET]

Yep you are right headspace has nothing to do with the locking lugs provided they are not worn.

I ran into an issue a few years back while reaming in a new barrel for headspace.

I will back up and tighten my shot group on that one. To repeat what you are saying. What can happen is when the rear of the locking lugs wear the headspace will be affected. Make sure there is no wear on the front of the locking lugs either.

If the back of the locking lugs wear then the case headspace on the .30 cal will move back. If you convert the dang thing over to tokarev 7.62X25 then you have the case shoulder to worry about now.

We understand how headspace works. How the cartridge fits into the chamber.

There should be consideration taken into effect when reaming a new barrel for headspacing.

These bolts were never intended to last past 6000 rounds of firing. There have been some that have lasted past that. The rear of the locking lugs on these bolts batter and take a beating. If I were to buy another M1 carbine I would do it through the Civilian Marksmanship program (CMP). They have armorers who inspect and replace every part and parcel of what they are sending out the door.
The M1 Carbine is what? Approaching 65-70 years old? You had better believe I would be inspecting that bolt for cracks around the locking lugs and wear at the back and the front.
If you are going to ream a new cartridge then use a very serviceable bolt with no wear on the locking lugs.
Get and use headspace gauges

 

[Jim Watson]

Back when carbines were $20 from the DCM through NRA, there were some wild and wonderful conversions made... or attempted.

The question would be, if you set the barrel back enough for the 7.62x25 chamber to clean up the .30 Carbine chamber, would there be enough metal in the operating slide to cut its contact surface with the gas piston back the same amount? If not, you would have to rebarrel as described by Dirtyjim. Perhaps you bush the chamber and recut in new metal.

Bolt faces and extractors have been opened up as large as .473" and I am sure gas ports have been drilled to suit the new caliber.

The key word here is "you." If you have the equipment and knowhow, it could be an interesting project on something like that Plainfield, where the collectors would not care about the originality and whether it were inspected by Alfred E. Neumann or Elwood P. Dowd.
If you would have to pay a gunsmith, prepare to be shocked, the cost would be high.

 

[dirtyjim]

one of the more interesting conversions was the universal .256 ferret.
it was chambered in .256 win mag. complete rifles bring as much or more than most usgi carbines.
barrel & magazines occasionally come up on gunbroker.
the .256 win mag was a .357 mag case necked down to .25 caliber.
factory loaded .256 win mag is no longer available but brass & dies still are. you can also make your own brass from .357 magnum cases.
if i ever decided to build an oddball carbine it would probably be in .256 win mag

 

[Travlin]

This sounds like a bad idea for all the reasons posted above, plus I'll add some more.

The GI specs called for non-corrosive ammo, which was unusual at the time. This was to protect the gas piston system; I believe because the design vented back through the barrel instead of a blow-off port. All .30 Carbine ammo has been non-corrosive except some old Chinese that was passed off in Lake City brass.

.30 carbine
Case length 32.76 mm (1.290 in)
Overall length 41.91 mm (1.650 in)

7.62x25 Tokarev
Case length 25 mm (0.98 in)
Overall length 34 mm (1.3 in)

The Tokarev is 0.35 inches shorter, but it is a bottle-neck cartridge so you would have to make your barrel thinner at the chamber which sounds hazardous.

How can you ever check the head space if you change it, since the standard gauges won't work?

If you shorten the barrel won't your front sight be canted since you have to screw the barrel further into the receiver? If it turns far enough you could cut a new channel in the barrel for the key that holds the sight, but that is a whole new job to mess with.

Like RC said, what do you hope to gain?

 

[Jim Watson]

I don't think it is a worthwhile idea unless, as I said, the OP has the capability of doing it himself just for the challenge. But except for the part about corrosive ammo in the M1 piston, your other objections don't amount to much.
There have been carbine conversions to much larger diameter cartridges with even thinner barrel walls. The .45 Win Mag may have been too much, but things like the .30 Kurz and .256 Ferrett seemed to do ok.
I fail to see why a regular 7.62x25 headspace gauge would not work.
Setting back the barrel on a gun with iron sights simply means doing it in full turns so the sight comes out on top. Carbine barrels are threaded 20 tpi so to get a completely clean chamber with a .31" shorter case (case length governs, not OAL), set back the shoulder and extend the threads 7 full turns. The possible hangup here would be whether he could modify the operating slide that much. Cut and weld, maybe.

 

[USSR]

This sounds like a bad idea for all the reasons posted above...

+1. It's the solution to a problem that doesn't exist.

Don

 

[Travlin]

Jim

You know more about this than I do. It seems someone with your level of knowledge could do it. But, I didn't get the impression the OP had thought through all the implications of such a change. Like you said, it would be an interesting technical challenge. But unless a person is very skilled I would expect the results would be to turn a good gun into an unreliable single-shot.

 

[Jim Watson]

Well, I do too. I would never try it myself.
The OP has to decide if it is worth his time, money, and risk to a usable gun.
As I said, when carbines were cheap, there were a lot of different things tried.
But it is just something to kick around on the board for us.