Shooting a .30-06 Bannerman Mosin

[Ian]

I took my life in my hands last weekend and put a few rounds through a Bannerman converted .30-06 Mosin (the actual firing starts at about 9 minutes in):

http://www.youtube.com/watch?v=KI7BCToQhRc

http://www.forgottenweapons.com/bannerman-30-06-mosin-nagant-video/

Bannerman was lot like the Century of their day; a huge surplus arms company. When they bought up surplus US-made Mosins in the early 1920s there was no domestic source for 7.62x54R, so they converted a lot of the guns to .30-06 for the sporting market. Conventional internet wisdom is that these conversions are pretty dangerous and liable to explode, but I don't think that is realistic.

The gun headspaced perfectly, and we found nothing when checking for overpressure signs. I was expecting a hopelessly inaccurate shooter, but it was actually pretty good (ammo was US M2 ball). The only target on hand was a 1/2 scale silhouette at 100 yards, and several shooters were making very consistent hits on it kneeling and offhand. If I was a hunter in 1925 I would have bought one. Certainly a lot cheaper than my Remington Model 8!

 

[Carl N. Brown]

The warning about the Bannerman conversion is the thinness of the metal left over the forward part of the chamber.

Since the 7.62x54R is fatter than the .30-06, the Mosin barrel was removed, the rear end of the barrel was lopped off, the barrel retreaded and chambered to .30-06, and reinstalled.

I have seen a cross-section drawing showing the .30-06 chamber in a converted Mosin barrel and it was scary to me.

 

[offthepaper]

Anyone know how many of the US made Mosins were converted to 30-06?

 

[Slamfire]

The warning about the Bannerman conversion is the thinness of the metal left over the forward part of the chamber.

Since the 7.62x54R is fatter than the .30-06, the Mosin barrel was removed, the rear end of the barrel was lopped off, the barrel retreaded and chambered to .30-06, and reinstalled.

I have seen a cross-section drawing showing the .30-06 chamber in a converted Mosin barrel and it was scary to me.

I agree.

Even without a wall thickness and stress analysis I am going to say that the reduction in chamber sidewall makes this conversion dangerous.

It is not appreciated but the barrel carries more load than the receiver. Load is surface area times chamber pressure and that barrel is housing a three inch long cylinder. The total load is much larger than what the lugs have to support.

Barrels carry load in the radial direction, such as shown in this picture.



Reducing the thickness of the chamber around the cartridge case is unwise.

 

[cal30_sniper]

Does anyone have a scan of that overlay showing the chamber of the .30-06 cartridge on the reduced shank Mosin barrel? I think that picture might tell a thousand words as to the safety of this conversion.

Ian, I sure hope you aren't ever planning on feeding commercial .30-06 through that rifle. The M2 ball ammo is not loaded that heavy, as it has to reliably function the Garand without hurting it. Commerical ammo might do some really bad things to an action that was already marginal with M2 ammo. I only ask because I found one of your threads from another forum last year where you said you never planned on firing the rifle.

Please bear in mind that doing something once does not mean it is safe. Metal fatigue is very much cumulative, and you have no idea what that rifle has been through with previous owners. Just because it didn't fail the first time you shot it, doesn't mean it won't the next. I've never seen one of these rifles in person, but your pictures of the extremely short barrel shank made my toes curl. With an '06, you are dealing with an extreme amount of pressure, and in this case, a very thin barrel.

Looking at cartridge dimensions, I can see why they didn't try to rechamber it to .30-40 Krag or .303 British, both of which would have been much safer. What I can't understand is why they went with .30-06 instead of .300 Savage. My guess is that a military surplus company probably didn't have any engineers on hand to tell them what a bad idea what they were doing was.

 

[NeuseRvrRat]

 

[cal30_sniper]

Wow, that is quite a bit scarier than I imagined.

Ian, I wouldn't shoot that rifle any more if I were you. You've tempted fate enough already.

I've got a 1939 production 6.5mm Carcano that was later cut down and rechambered to 8x57 by H&K in Germany as a last ditch defense weapon. My Great-Grandfather traded it off of some Mexicans in Presidio, TX a long time ago. I've never fired it, and you couldn't pay me enough to, for the exact reason shown above. That Carcano has one of the thinnest barrels that I've ever seen, but the critical area of that bannerman conversion adjacent to the chamber is much worse in comparison.

 

[Carl N. Brown]

Anyone know how many of the US made Mosins were converted to 30-06?

From what I have read, even dedicated collectors and historians of Bannerman are not sure.

 

[hang fire]

If thin wall chambers are dangerous, guess we should destroy all our high pressure lounden banger revolvers.

 

[kBob]

While in high school I had a local dealer actively hunting one for me.

I planned to shoot GI ammo in it.

Now that I have you all riled up.....I was planning on using it as an Agressor rifle (Opposing Force in military training) and use the same US .30 cal blanks in it we used in our M-1 Garands.

I did use an bring back M44 for one session, but my attempt to make a blank using a 7.62x54 primed case and the powder from a GI .30 blank and painted in card board stopper failed for whatever reason. That M44 was the first Mosin I ever fired and even with ancient US hunting ammo it was a painful experience for someone used to rimfires and M-1 carbines.

-kBob

 

[cal30_sniper]

If thin wall chambers are dangerous, guess we should destroy all our high pressure lounden banger revolvers.

Your what?

I have a hard time imagining any revolver other than a .454 Casull could match the 60,000psi of commercial .30-06 loads.

 

[Scooter22]

"Looking at cartridge dimensions, I can see why they didn't try to rechamber it to .30-40 Krag or .303 British, both of which would have been much safer. What I can't understand is why they went with .30-06 instead of .300 Savage. My guess is that a military surplus company probably didn't have any engineers on hand to tell them what a bad idea what they were doing was."
__________________
Because they had allot of surplus 30-06 to sell.

 

[Ian]

I suspect the reason they didn't use .300 Savage is because it was basically brand new at the time. The caliber conversion was to use a cartridge that was popular and widely available, and while .300 Savage would have fit the bill in the 40s or 50s, it didn't in the early 20s.

 

[Ian]

FWIW, the M2 ball I was shooting has a chamber pressure of 50k psi, which is actually below the 7.62x54R standard of 52k psi.

 

[hang fire]

Your what?

I have a hard time imagining any revolver other than a .454 Casull could match the 60,000psi of commercial .30-06 loads.

Good luck putting a 60,000 psi 06 load in a Model 95 Winchester.

 

[cal30_sniper]

Good luck putting a 60,000 psi 06 load in a Model 95 Winchester.

How about answering the first question before starting off on a new tangent?

While extended use of high pressure loads are not recommended in the original 1895 rifles, the modern reproductions are more than capable of using them, mainly through the use of better steels. Even so, the use of full power .30-06 loads in an original 1895 will cause peening and bolt face setback, resulting in excessive headspace. This is bad for the rifle, but not dangerous to the shooter unless a grossly excessive headspace is allowed to proceed unchecked. Quite different from the scenario where the front receiver ring or barrel shank explodes in the Bannerman.

FWIW, the M2 ball I was shooting has a chamber pressure of 50k psi, which is actually below the 7.62x54R standard of 52k psi.

Correct, as I earlier mentioned, shooting M2 ball makes this a very unsafe operation instead of an extremely unsafe proposition. If I'm not mistaken, CIP standard for the 7.62x54R is actually 57ksi. However, think of it this way. You are firing a cartridge that is very near the maximum pressure for the original design, but you are doing it with what looks like more than 50% of the metal removed from one of the most critical areas of the original design.

Every time you fire any rifle, the metal expands and contracts around the chamber. Steel is elastic just like any other metal, and has a stress-strain curve. At a certain point in the expansion, the metal ceases to become elastic (i.e., returning to its original shape), and becomes plastic (will not return completely to its original shape). This is exactly what leads to excessive headspace when firing high pressure loads in older rifles. In the case of the bannerman, with all that reinforcement around the chamber removed, if the metal is reaching plastic deformation, it could very well fail altogether.

Not to mention that you are operating with a factor of safety that is much, much lower than originally designed. Rifles are over designed, because cartridges are often accidentally overloaded, even from the factory. If you take away this extra factor of safety, you are shooting a ticking time bomb that is waiting for the first out of spec ammunition to come along and kill you.

At the time the rifles were introduced, the use of early smokeless powders resulted in lower pressure ammunition than we see today. This is why the M2 ball is only about 52ksi. Later on, with much more advanced powders, designers were able to duplicate the performance of M2 ball out of the much smaller .308 Win case. Those same advanced powders were used in the .30-06, resulting in improved performance, but higher pressures than originally conceived. While the Bannermans may have been marginally safe to shoot when they were introduced, age, misuse, and the introduction of higher pressure commercial loadings is exactly the reason they SHOULD NOT be fired today. What little factor of safety they originally had is most likely completely gone at this point. The only reason you probably haven't heard of one blowing up yet is that wisely, nobody else is shooting them, due to the ample warnings in existence.

In the end, its your rifle, and you can choose to do with it as you want, at the risk of your own life and limb. I only take issue with the idea that since you fired it a few times, it must be safe. That is simply not true. Even if the chamber was only slightly deforming each time the rifle was shot, the life of that arm could currently be measured in the tens of rounds or single digits, especially if you were ever to start firing .30-06 commercial rounds. Think of what the uninformed could do with such information before making blanket claims about the safety of a rifle which so many people over the years have advised against firing.

 

[cal30_sniper]

I suspect the reason they didn't use .300 Savage is because it was basically brand new at the time. The caliber conversion was to use a cartridge that was popular and widely available, and while .300 Savage would have fit the bill in the 40s or 50s, it didn't in the early 20s.

That makes sense. What a shame, because chambering in 300 Savage would have left a lot more meat in the barrel shank, pretty much eliminating any safety concerns of the Bannerman. Its also a unfortunate that all the other contemporary rimmed .30 cal cartridges are so narrow compared to the 7.62x54R. If they had been able to convert these to .303 Brit, .30-40, or .303 Savage, it would made a heck of a handy little sporter.

 

[Gunnerboy]

All im gonna say about these sweet conversions is 06 loaded subsonic is quite entertaining thru them.

 

[Lj1941]

Grenade

It looks to me like a grenade with the pin pulled and ready to blow.This is from a person who has 2 UNMODIFID 91/30S that I shoot every chance that I can!.

 

[cal30_sniper]

I've done some back of the envelope calculations to amplify my point.

Here's the assumptions:

1. The barrel can be modeled as a thick-walled pressure vessel.

2. The critical point is at the throat or neck of the cartridge. In the Bannerman, this is the point where the barrel has already stepped down to the thin section, but the chamber is still large enough to allow the neck of the casing to enter.

3. The inner radius at the neck of the casing is ~0.34". This is from the neck diameter of a fired .30-06 case.

4. The outer radius at the thin part of the barrel is ~0.75". I don't know this, I'm just guessing.

5. The outer radius at the thick part of the barrel of a regular mosin is ~1.1". Again, I don't know this, it's just a guess.

6. A military 7.62x54R has a maximum chamber pressure of ~52ksi.

7. A commercial .30-06 round has a chamber pressure of ~60ksi.

The Method:

I will look at the hoop stress present at the point that is halfway between the inner and outer radius of the barrel at the critical point. That is 0.38" from the centerline of the Bannerman barrel, and 0.72" from the centerline of a regular Mosin barrel.

The Results:

Using the equations for a thick walled pressure vessel, I get a hoop stress in the Bannerman barrel of 44.9ksi, vs a hoop stress in the Mosin barrel of 18.3ksi. That means, firing a commercial .30-06 cartridge through a Bannerman rifle, you are exceeding its original design parameters by approximately 250%.

Using the same equations, but assuming an M2 ball pressure of 50ksi, you get a hoop stress of 37.4ksi. This is still ~205% of the original design parameters of the Mosin barrel.

Finally, lets look at the hoop stress present at the outer edge of the barrel for all three cases:

Standard Mosin, 7.62x54R: ~11.0ksi
Bannerman, M2 Ball: ~25.9ksi (235% original design parameters)
Bannerman, .30-06 Commercial: ~31.0ksi (~280% original design parameters)

Now do you see the danger?

EDIT: I found the actual diameters for the counter of a Mosin barrel. The outer diameter of the barrel at the end of a chamber of a regular 7.62x54R Mosin is 1.139". The outer diameter of the thin part of the barrel at the throat of a .30-06 Bannerman is 0.776". This leads to the following numbers:

Hoop Stress at inner surface of the barrel (0.340" from bore centerline):
7.62x54R Mosin: 62.2ksi
M2 Bannerman: 73.7ksi (118%)
.30-06 Bannerman: 88.5ksi (142%)
Double-charged 7.62x54R Mosin (104ksi chamber pressure): 124.3ksi (200%)

Hoop Stress at the middle of the thickness of the barrel (i.e., halfway between the inner and outer radius)
7.62x54R Mosin: 17.1ksi
M2 Bannerman: 34.9ksi (204%)
.30-06 Bannerman: 41.8ksi (244%)
double charged 7.62x54R Mosin: 34.3ksi (200%)

Hoop Stress at the outer surface of the barrel
7.62x54R Mosin: 10.2ksi
M2 Bannerman: 23.8ksi (233%)
.30-06 Bannerman: (279%)
double charged 7.62x54R Mosin: 20.3ksi outer (200%)

As you can see, the outer half of the barrel of a Bannerman is experiencing more stress than a regular Mosin Nagant fired at twice it's normal chamber pressure, even when using M2 ball. NOT SAFE!

 

[cal30_sniper]

Cliff Notes:

Unless you feel comfortable regularly shooting a double charge through your Mosin Nagant, don't fire the Bannerman anymore.

Keep in mind the method of failure here is not the bolt lugs or receiver ring shearing (that would most likely be what happened if you fired a double charge through your Mosin). The method of failure here is the barrel shearing. In this case, the bolt face and receiver ring only see the slight increase of .30-06 pressure, which is well within their design limits, because their dimensions haven't changed. The dimensions of the barrel relative to the chamber HAVE changed, and thus they are under much more stress even though there is only a marginal increase of pressure (or negligible change of pressure in the case of M2 ball).

Now, unless you really feel comfortable about that original military barrel with 100 year old metallurgy being able to handle 200-300% of its original stress, DON'T SHOOT IT ANYMORE. There's a reason that Magnum cartridges have thicker barrels, and it has nothing to do with recoil reduction...

 

[Ian]

Clearly, there is a need for more research, IMO. I don't dispute your calculations, except that the original major dimension of the barrel is assumed to be sized based on safety requirements. The barrel is that big because of the additive dimensions of the cartridge case head plus locking lug width plus barrel thread depth.

I need to see if I can get my hands on equipment to actually measure the strain on the barrel shank during firing - that would pretty conclusively decide the question.

It could be calculated, too, if we knew the material spec for a Remington Mosin barrel (I don't)...

 

[cal30_sniper]

Correct, the critical piece of information is what the original Factor of Safety of the design was. However, notice that the original barrel shank stays at a large diameter far past the locking lugs, threads, and cartridge case body. That is because this area of the barrel in particular has to sustain the high level of pressure of the powder burning in the case before the bullet has begun to travel down the barrel. As the bullet travels, powder volume expands drastically, and pressure drops. In the bannerman, the area of the barrel designed to sustain this dropped pressure now has to handle the full chamber pressure.

The barrel shank is a very critical area. If the shank could safely be turned down and still handle the full pressure of the round, you would see virtually every rifle in existance doing that. The weight savings would be fairly significant. Yet we don't see that happening anywhere in the industry. That alone should tell us something. For even a Featherweight contour barrel, you still see 2" of shank, followed by another 3.5" to taper down to the .700" starting contour of the barrel. In comparison, a regular Mosin barrel has 2" of shank, with a 0.5" taper to the .776" starting diameter. This is already a very light barrel comparatively, but it was designed for a moderate pressure cartridge, and is more than adequate. The Bannerman barrel, however, only has a ~1.25" shank, with the same 0.5" of taper. This is far shorter than anything else out there. If it was safe to cut a barrel down like that, I would think the manufacturers would be using it in featherweight rifles to save weight.

As you said, there is no way to determining the strain other than measuring it. We have no idea what the metallurgical properties are for steel that Remington was using nearly 100 years ago to make military rifle barrels. We can safely assume that given the practices and knowledge of the times, it is definitely inferior to rifle barrel steels in use today. Yet we still don't see barrels that thin, even on modern rifles.

Simply put, you are pushing that rifle far, far beyond its intended limits. You are literally one imperfection, impurity, or ammunition variance away from making the situation even worse. The numbers alone show that the outer half of the barrel is under the same amount of stress as a double-charged load. We've all seen what a bad load does to the shank of a rifle barrel. It bursts it. Having a thinner wall stresses much of the barrel in exactly the same way. If at any point, some inner region of the barrel reaches the ultimate strength, or enough of it reaches the yield strength, the rest of it is going to let go rapidly. The one saving grace of the M2 ammo is that it keeps this inner region relatively low (although still higher than the factory 7.62x54) due to the nature of its reduced chamber pressure. However, the higher chamber pressure of 60ksi .30-06 greatly increases the chance of yield or ultimate strength being reached in the inner barrel regions, which would be rapidly followed by failure in the outer barrel regions due to the nature of their already overstressed condition.

 

[cal30_sniper]

Also, keep in mind that there are multiple stress risers in the form of the end of the neck of the chamber (a fairly sharp reduction from 0.340" to approx 0.310"), as well as the edges of the rifling itself, which start immediately in the vicinity of the critical point where the reduced barrel diameter and chamber neck meet. That further exacerbates the over-strained situation present in the rifle barrel.

 

[cal30_sniper]

I found an old volume of the Iron Age, published in July 1919, that gives the specifications of barrel steel used in the 1903 Springfield. Although not identical to the Remington made Mosins, I think we can all agree that the properties would be very, very similar, given that they were made by the same industry, within a few years of each other, and almost certainly out of the same materials and processes.

Ultimate tensile strength is listed as 110ksi. Yield Strength is listed at 75ksi.

What this means, is that given the numbers I calculated earlier, you are nipping at the heels of the yield strength in the inner regions of the barrel using M2 ball in a bannerman rifle. Using a 60ksi load, you have already surpassed the yield strength, and are well on your way to surpassing the ultimate strength. Bad idea.