M91/M91-30 Hex receiver strenth

[harryhall]

I am new to forum and I can emagine that this topic has came across before. But, I have scaned the web trying to find just how strong these great actions are. I have noted that the max chamber psi is 56,000. Yet I can find no technical studies on this receiver. Now, I know about the distructive test that people have conduted,but what about actual certified government or certified civillian test.
Thanks

[Junk Yard Dog]

I am sure such information exists and such tests were done, however the information would be buried in some Russian or Finn archive and in those languages. Remington made many M91's here in the USA during the Great War, they may have done tests on the receivers, you would have to contact the Remington company to find out if their archines go back that far. I have never heard of a Mosin receiver blowing if correct ammo was used ( or at all for that matter) they tended to last for generations, and be reused over and over again. When old rifles wore out the receiver was reused to build new rifles, they held up very well.

[Ratnik]

Since 1940 barrels were tested at factories with VD cartridge, that provided 4200 atmoshpheres pressure, and complete rifles with two high pressure cartridges that provided 3200 atmospheres pressure. Before 1940 barrels were tested with with powder test that prodided pressure up to 5400 atmoshpheres

[Junk Yard Dog]

There you go, now if you were planning on doing something crazy like loading cartridges to maximum velocity and beyond, don't. There is no need for that when the 7.62x54 is already a match for the .30-06 with it's normal 148 grain bullet and powder loads. No need to torcher rifles that could be using century old parts.

[harryhall]

Ratnik, guess you have awnserd my question. By the way, what is a VD cartridge and why were complete rifles tested at less psi after 1940? Maybe a WWII thing. And no, I do not intend to run a hot load. I like mosin nagant just like it is.
Thanks

[steelbuttplate]

Ratnik, guess you have awnserd my question. By the way, what is a VD cartridge and why were complete rifles tested at less psi after 1940? Maybe a WWII thing. And no, I do not intend to run a hot load. I like mosin nagant just like it is.
Thanks

I don't reload anymore, but that's a good rule of thumb for everybody.... It's already a hot load

[AMCHornet]

Since 1940 barrels were tested at factories with VD cartridge, that provided 4200 atmoshpheres pressure, and complete rifles with two high pressure cartridges that provided 3200 atmospheres pressure. Before 1940 barrels were tested with with powder test that prodided pressure up to 5400 atmoshpheres

This is great information that I'd like to clarify a little bit with you. I understand the following from what you said:

1. Pre-1940 barrels with no receiver attached were proof tested at 5400 atmospheres, or 79,300 pounds per square inch.
2. Post-1940 barrels with no receiver attached were proof tested at 4200 atmospheres, or 61,700 pounds per square inch.
3. Complete rifles (barrel with receiver) were proof tested at 3200 atmospheres, or 47,000 pounds per square inch.

The C.I.P. maximum pressure for the 7.62x54r is 56,565 PSI, and by C.I.P. regulation the rifle must pass a 125% overpressure proof test of 70,706 PSI. By your information, only pre-1940 barrels pass that test. How can that be?

This numerous proof marks seen on barrels and receivers almost certainly refer to some of these tests. The only question is: which proof marks refer to which test?

[entropy]

AMC Hornet- There are MG rounds for aircraft MG's that should not be shot in Mosins. There were threads about them on the forum somewhere. Perhaps they are loaded to those pressure levels.

Many US 'gun guys' over the years proclaimed the Mosin cannot be a strong action, due to the split receiver, but they are plenty strong enough , though the down side of the design is with overpressure loads, the main gas venting is straight in the shooter's face.

[Ratnik]

Ratnik, guess you have awnserd my question. By the way, what is a VD cartridge and why were complete rifles tested at less psi after 1940? Maybe a WWII thing. And no, I do not intend to run a hot load. I like mosin nagant just like it is.
Thanks

Powder test was obsolete and difficult procedure. Special threading for a plug was cut at the barrel blank, it took many time. Test of the complete rifle with cartridge was much more simple. VD cartrighe mean "Высокое давление", high pressure. It was considered that such pressure was enough to indicate defects of metal. That's how it is explained in the 1938 document that I have. And barrel blank for powder test was thicker than finished barrel, so it can hold gigher pressure.
To be more clear, exact name of the VD cartridge is "High Pressure" cartridge, cartridges that were used for tests of the assembled rifle are "strengthened cartridges".


Pressure curve (line #I) in the barrel blank during powder test. At the left - pressure in kg per square cm

2.2.25.jpg

The C.I.P. maximum pressure for the 7.62x54r is 56,565 PSI, and by C.I.P. regulation the rifle must pass a 125% overpressure proof test of 70,706 PSI. By your information, only pre-1940 barrels pass that test. How can that be?

This numerous proof marks seen on barrels and receivers almost certainly refer to some of these tests. The only question is: which proof marks refer to which test?

I forgot to mention that receivers were tested before assembly with press machine test - pressure was 6560 kg for the receiver recoil recesses, and for the bolt head it was 8200 kg.

Barrel markings:
П in circle - powder test (Tula rifles have this marking also in 1942-1944, but in fact they were tested with VD cartridge)
Y in circle - VD cartridge test
O in circe or OO - streghten cartridge test of the complete rifle

П or O in circle at rifle parts - press or another machine test

[AMCHornet]

This is awesome information, Ratnik. Thank you so much for sharing this with us. Having forum members in Russia or Ukraine like yourself who have access to the original information and documents on these rifles is so helpful for the rest of us.

[Ratnik]

besides, there were rifles pressure measurment devices

20180713_223412.jpg

[AMCHornet]

Ok, I want to make sure I have this right.

Pre-1940:

1.) Receivers were tested in a press machine to a mechanical pressure of 6560 kg for the receiver recoil recesses, and 8200 kg on the bolt head. A "П in a circle" or "O in a circle" proof mark on the receiver may indicate these press or machine tests.
2.) Roughly machined barrel blanks without receivers attached were "black powder tested" to 5400 atmospheres, or 79,300 pounds per square inch and marked with a "П in a circle" proof mark on the barrel shank.
3.) Finished barrels and receivers assembled together into a complete rifle were tested with two "strengthened cartridges" to 3200 atmospheres, or 47,000 pounds per square inch and marked with an "O in a circle" of "00" proof mark on the barrel shank.

Post-1940:

1.) Receivers were tested in a press machine and proof marked the same as pre-1940.
2.) Finished barrels with no receiver attached were tested with a VD "high pressure" cartridge to 4200 atmospheres, or 61,700 pounds per square inch and mared with a "Y in a circle" proof mark on the barrel shank.
3.) Finished barrels and receivers assembled together into a complete rifle were tested with two "strengthened cartridges" the same as pre-1940.

So really the only thing than changed in 1940 was the switch from doing the powder test to barrel blanks to doing a VD cartridge test of finished barrels.

Is all that correct?

[Lavitias]

So is it safe to say with all this info as long as your not doing something stupid like putting say range trash into the cartridge full to the brim and then shoving a projectile into that and compressing it. That your probably not gonna blow your Mosin up. Not that you should try that scenario with any firearm.

[AMCHornet]

Well....an overpressure may not blow the gun the first time but do it over and over again and the repeated fatigue to the steel could eventually cause a failure. It adds up.

That being said, when was the last time you heard of somebody reconfiguring their face by blowing up a Mosin-Nagant? Never. I'd say they have a good safety margin. Russian firearms have a reputation of being massively overbuilt. Strong like Bull. They're not P14 Enfield strong, but they are strong.

[Lavitias]

I was gonna say that also Hornet that I've never heard of someone doing redneck plastic surgery on their face. But I also said you shouldn't be doing stupid things with reloads either. I.E if the load calls for 45.5 grains of Varget you probably shouldn't be going well if I get that with this what's 2 more grains gonna do. Well unless you wanna look like Wiley Coyote after he played with explosives.

[Junk Yard Dog]

Well....an overpressure may not blow the gun the first time but do it over and over again and the repeated fatigue to the steel could eventually cause a failure. It adds up.

That being said, when was the last time you heard of somebody reconfiguring their face by blowing up a Mosin-Nagant? Never. I'd say they have a good safety margin. Russian firearms have a reputation of being massively overbuilt. Strong like Bull. They're not P14 Enfield strong, but they are strong.

The P14 Enfield like the US1917 it became has a problem with receivers cracking around the ring. The cause of this was a failure to properly chase the threads when rebarreling during the WW2 refurbs coupled with a somewhat brittle receiver that is so hard it cracks instead of stretches under extream overpressure. The receivers later came to be used when building magnum sporters so apperantly the stress caused by forcing a slightly off spec thread barrel over rust in the threads is higher than a 500 magnum wizz bang super special elephant cartridge puts on the steel. This is why should you have an Enfield with anything but the original Great War era dated barrel on it you pull the action and glass that ring closely. A good example of the slip shod work that was being done by the various contractors assigned the job of refurbishing the 1917's before sending them to our allies is one I have. High Standard barrel that is of excellent quality, but the contractor failed to properly allign the front sight base, it's canted ever so slightly to the right. That sort of work is the hallmark of the rush job.

[Ratnik]

Ok, I want to make sure I have this right.

Pre-1940:

1.) Receivers were tested in a press machine to a mechanical pressure of 6560 kg for the receiver recoil recesses, and 8200 kg on the bolt head. A "П in a circle" or "O in a circle" proof mark on the receiver may indicate these press or machine tests.
2.) Roughly machined barrel blanks without receivers attached were "black powder tested" to 5400 atmospheres, or 79,300 pounds per square inch and marked with a "П in a circle" proof mark on the barrel shank.
3.) Finished barrels and receivers assembled together into a complete rifle were tested with two "strengthened cartridges" to 3200 atmospheres, or 47,000 pounds per square inch and marked with an "O in a circle" of "00" proof mark on the barrel shank.

Post-1940:

1.) Receivers were tested in a press machine and proof marked the same as pre-1940.
2.) Finished barrels with no receiver attached were tested with a VD "high pressure" cartridge to 4200 atmospheres, or 61,700 pounds per square inch and mared with a "Y in a circle" proof mark on the barrel shank.
3.) Finished barrels and receivers assembled together into a complete rifle were tested with two "strengthened cartridges" the same as pre-1940.

So really the only thing than changed in 1940 was the switch from doing the powder test to barrel blanks to doing a VD cartridge test of finished barrels.

Is all that correct?

Yes, generally it is correct. Elimintaion of powder test occured in mid 1940. Tula already stopped production of m91/30 rifles. Interesting, that at first Y on circle marking was small, and it not all 1940-early 1941 rifles have it (maybe it is somewhere under the wood).
I did not came across detaled info about press machine tests in 1940's so can't state that they remained the same.

Early small Y in circle

DSC_1031rs.jpg

RT2_1781.jpg

Late big Y in circle

IMG_0565.jpg

No marking

13319070774_33f5da4a81_o.jpg

Press machine test marking (Tula)

post-65751-0-74524900-1524326102.jpg

[AMCHornet]

Yes, it seems like they skipped out on stamping a lot of the wartime production rifles with the proof marks, stamped them in unusual places, or the stamp is illegible. I've noticed that on my own rifles.

[SA1911a1]

Well....an overpressure may not blow the gun the first time but do it over and over again and the repeated fatigue to the steel could eventually cause a failure. It adds up.

That being said, when was the last time you heard of somebody reconfiguring their face by blowing up a Mosin-Nagant? Never. I'd say they have a good safety margin. Russian firearms have a reputation of being massively overbuilt. Strong like Bull. They're not P14 Enfield strong, but they are strong.

If you want to do a comparison of receiver strength you use the Japanese type 99 as your gold standard. Post war testing showed that those rifles would take charges that would junk '03s, Mausers, Enfields or Mosins.

[Ratnik]

Yes, it seems like they skipped out on stamping a lot of the wartime production rifles with the proof marks, stamped them in unusual places, or the stamp is illegible. I've noticed that on my own rifles.

Oh, I forgot about wartime problems. Inspite it was supposed to use 2 strengten cartridges for tests of the complete rifles, in late 1941-early 1942 Izhevsk factory used only one because of lack the cartridges, and in 1941 at Tula factory because of lack of VD cartridges they used strenghten cartridges, heated up to 60 degree Celsius