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1895 Nagant vs Modern Revolver Design

1895 Nagant, TT-30, TT33 and Makarov
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1895 Nagant vs Modern Revolver Design

#1 Post by RWS » Mon Jun 26, 2017 9:39 am

For those of you out there that own a Nagant revolver, it is good to recognize that it works on timing principles that are very different from modern revolvers. I thought it might be good to briefly look at these differences.

A "modern" revolver, ala S&W, Ruger, etc., works by precisely timing the cylinder to rotate 1/6 of a turn (for 6-shot revolvers) and bringing the chamber mouths of the cylinder in line with the barrel. It is difficult to get perfect alignment on all cylinders. It can be done but it would raise the cost of the revolver significantly if they were to be manufactured so that the cylinder and barrel were perfectly aligned on all cylinders.

The workaround here is the concept of the forcing cone, essentially a funnel to cam the projectile into perfect alignment with the barrel. If a revolver is significantly out of time then even the funnel effect will not be enough and the bullet will hit on the edge of the forcing cone causing the revolver to "spit" lead out to one side or the other. Most experienced shooters know all this.

The point is that this is NOT the way a Nagant revolver works. First and foremost, a Nagant revolver does NOT have a forcing cone. It is more of a counterbore. A counterbore is basically a perfectly round hole with a flat bottom, and that's what the barrel extension is. In the center of this flat bottom is a smaller hole, which is the barrel. So, the larger hole is in the barrel extension that gets inserted into the cylinder when the revolver is cocked, and the smaller hole is the barrel itself.

So here's the key point... When the barrel extension gets inserted into a loaded cylinder, it is using the case body as a self-centering device so that the cartridge becomes almost perfectly aligned with the barrel. To effect the gas seal, that cartridge has to be slightly longer than the cylinder.

Now we come that weird crimp on the top. If the bullet was simply inserted into the case and NO crimp was applied then the revolver could only be cocked if the cylinder rotated exactly 1/7 of a turn. Anything other than exactly 1/7 of a turn means that the barrel extension would hit on the edge of the case and it would only be possible to fully cock the gun at that point by assisting rotation with the weak hand. Many Nagant shooters have experienced this effect, myself included.

The weird crimp on the Nagant cartridge is a crutch. The smaller diameter of the crimp is designed to funnel or cam the cartridge into perfect alignment. Note that when cocking, the Nagant cylinder rotates first and moves forward second, so if there is slight misalignment between the barrel extension and cylinder then you may notice a slight extra rotation of the cylinder (caused by the case crimp camming the cylinder) as it goes fully forward into battery.

When the Russians refurbished all those Nagant revolvers, many of them received replacement cylinders. For the revolver to work smoothly, the inside diameters of the barrel extension and the cylinder mouths need to be as identical as possible. If the cylinder mouths are even slightly smaller than the inside of the barrel extension then the portion of the case inside the barrel extension will end up LARGER than the cylinder mouths.

This explains why ejecting cartridges for some Nagants on certain cylinders requires excessive effort. You are partially resizing the larger case mouth as you attempt to retract it through the smaller cylinder mouth.

If you've followed and digested all this then it should become apparent that shooting any ammo that is shorter than the cylinder is going to be something of a crap shoot. Many people use .32 S&W Long cartridges in their Nagants because it's often cheaper and/or easier to find one or two boxes of it than locating 7.62x38R ammo at the local gun store. Sometimes this works OK and sometimes shooters experience heavy leading and/or lead spitting because the cylinder and barrel are not in alignment. Remember, the Nagant has no forcing cone to correct misalignment.

The 7.62x38R case is tapered. .32 S&W, .32 S&W Long, and the .32 H&R Magnum are all straight-walled cases. It should make sense that the longer a straight-walled case is, the closer the exposed bullet will be to the internal walls of the tapered cylinder and the better the alignment will be. So, on any given Nagant revolver, the short .32 S&W case will not self-align nearly as well as the .32 H&R Magnum case.

It is important to note though that although the .320 Federal Magnum will insert and fire in a Nagant revolver, it generates close to 40,000 PSI and should never be fired in a Nagant. Even the .32 H&R Magnum should be considered essentially a +P round as it operates in the 20,000 PSI range. The Nagant nominally operates at or near 16,000 PSI. Because of all the unique design features of the Nagant revolver then I think it makes the most sense to stick with 7.62x38R ammo, but if you're using something else and it's working for you then, hey, run with it.

I don't really want to write a book here but I thought it might be helpful to share some of the things I've learned through futzing with these old guns. All comments, opinions, and lamentations can be entertained at this time.

-Bob

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Re: 1895 Nagant vs Modern Revolver Design

#2 Post by B32dominator » Mon Jun 26, 2017 10:31 am

Very interesting, the surplus ammo I have does not have the crimp at the top like the new production ammo does but I do believe the case is tapered down to the same specs at the mouth. My cylinder appears original to the gun. A previous Nagant I owned was not and it was a bear to unload.

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Re: 1895 Nagant vs Modern Revolver Design

#3 Post by RWS » Mon Jun 26, 2017 10:42 am

B32:

Yeah, you will find crimps that vary somewhat but the bottom line is that the slight variation is unimportant so long as it works to cam a cartridge into alignment so the cylinder can move fully forward.

Also, grab a magnifying glass and take your cylinder out. The original WW2 and earlier cylinders were cut to length by lathe turning. The post-war replacements were milled. If you see circular or slightly spiral tool marks on the face of the cylinder (similar to the grooves in an old vinyl record) then it was lathe-turned and probably original. If the tool marks are in a straight line then it is a post-war replacement cylinder that was milled and would be force-matched to the frame's S/N.

For the record, most cylinders have been replaced I think.

-Bob

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Re: 1895 Nagant vs Modern Revolver Design

#4 Post by B32dominator » Mon Jun 26, 2017 12:41 pm

I'll check that out, I know there are some matching marks but I'll have to take a look at it closer for which type.

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Re: 1895 Nagant vs Modern Revolver Design

#5 Post by B32dominator » Wed Jun 28, 2017 12:28 am

Circular grooves, plan on shooting it this weekend. We'll see how she runs.

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Re: 1895 Nagant vs Modern Revolver Design

#6 Post by B32dominator » Sun Jul 09, 2017 8:54 am

Got out the Nagant last weekend she shot better than I do with a revolver. Got issue with the cases getting stuck in just on cylander. Same cylander each time, other wise the other rounds mainly slid out of a slight push from the mouth. Wondering if I could polish up the cylander that's getting stuck or are is this a more involved process?
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Re: 1895 Nagant vs Modern Revolver Design

#7 Post by RWS » Sun Jul 09, 2017 11:25 am

If it's stuck so badly that you have to pound the ejector rod with your hand (and it actually hurts your hand a bit) then I can almost guarantee you that it is not a problem that polishing will fix.

I have a 1944 Ishevsk revolver where 3 of the cylinders constantly stick. As noted in my previous post above, the problem comes about when you fire the gun and the barrel recess where the end of the cartridge goes when the cylinder is pushed forward is larger in diameter than the front of the chamber being fired. The end of the case that protrudes out of the cylinder flares out when fired and becomes larger than the chamber diameter. When you try to push the empty case out it essentially has to resize the case that last 1/8 inch or so as it retracts back through the cylinder, and that is what you are perceiving as "sticking"

I view sticking as more or less a friction thing. Your/our problem is more of an interference fit at the case mouth, a sort of the snake swallowing the egg kinda thing and not a roughness issue.

To confirm this, field strip and clean the revolver thoroughly. Identify the bad chamber. Use or borrow a set of dial or electronic calipers and measure the inside diameter of the problem chamber at the front end of the cylinder and compare it with the inside diameter of the barrel recess.

Now... what you ideally want to see is that the inside diameter of the suspect chamber mouth is the same as or slightly larger than the inside diameter of the barrel recess. If my theory is correct, the 6 chambers that DON"T stick will have chamber mouths that are a few thousandths of an inch LARGER than the inside of the barrel recess. On these, the case mouth will flare inside the barrel recess but it's still smaller in diameter than the chamber mouths and so extraction effort is minimal to none.

BUT... on that one problematic chamber my guess is that the chamber mouth diameter is slightly SMALLER than the barrel recess diameter so that when you try and extract that case the case mouth is too large to pass backwards through the chamber. By the use of force you basically resize that case mouth as the case travels in reverse to extract.

For what it's worth, I have confirmed that the 3 bad chambers in my Ishevsk have undersize chamber mouths, which is why I THINK I know what your problem is. Could be wrong though. If I am right then you can ream the bad chamber mouth out to match the diameter of the ones that DON'T stick. Or, you can just mark the bad chamber and use the gun as a six-shooter.

Hope this helps.

-Bob

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