Mosin Nagant to 45-70?

[BattleRifleG3]

I've wanted a 45-70 bolt gun that has decent capacity (ie 4-5, not 2 like the Gibbs SMLE conversions) and figured maybe the Mosin Nagant is the best choice due to its magazine interruptor and bolt face.

The bolt face would take a little bit of lathe work, with its inner face turned flat, taken 0.007" deeper, and opened up 0.02" in radius.

Am I correct that the barrel would need to be threaded for the Mosin action? Could the receiver possibly have the threads turned off and have the barrel pressed and pinned instead, since the 45-70 is such a low pressure round?

I'm wondering what the weakest link of this would be that would limit handloads.

[John Traveler]

BattleRifleG3,

I felt the hairs on the back of my neck standing up as I read your idea of boring our the receiver threads, pressing & pinning a barrel in place.

TRUST ME, it's NOT a good idea to install a large-calibre centre-fire barrel like that, not even a modest pressure round like the .45-70!!  

Only the cheapest .22 LR and .410 shotguns use pressed-and-pinned barrels as you described.  A very few .22 Hornet rifles were made that way, come to think of it, and even they did not hold up to continued use.

Your idea of a .45-70 Moisin-Nagant rifle is a feasible one, but only if you properly fit a barrel.

John

[Rojelio]

I think some of the AKs and SKSs with stamped receivers had pressed and pinned barrels. How much pressure do they generate? Rojelio.

[John Traveler]

The SKS receivers have always been machined forgings with the barrels screwed in as far as I know.  It was designed and used by the Soviets as the tactical equivalent of the US M1 Garand; i.e. a durable service rifle.

True, pressed-and-pinned barrels are standard construction for stamped steel AK rifles, but there are considerable differences:

1.  The AK-47/AKM series are "throwaway" service rifles.  The design gives a poorly trained conscript tremendous firepower, an effective, reliable weapon that requires little or no maintenance, and who's user is likely to be killed or captured quickly.  Service life was anticipated to be very short.  Accuracy and durability were not design features.

2.  The 7.62x39 military round operates in magnum pistol presssures (high 30K-low 40K range).  The much smaller cartridge base (compared to the full-size rifle), the lighter bullet, plus the semi-auto gas system results in reduced bullet dwell time, and lowered overall breech stress.  The design is famous for reliability under all operating conditions because of the low receiver stress.  The AK is also made with mild steel except for the breech extension and barrel.  Try that with full-caliber service rifles!

3.  Many service AK rifles also have excessive headspace but remain serviceable because standard ammunition is steel-cased, which absorbs some of the load from firing with excessive headspace conditions.  Steel cases have more tensile strength than brass cases.  The entire weapon and ammunition system are designed for war-time production expediency.

4.  AK armourers routinely restake receiver rivets and barrel pins in overhauling service weapons.  Imagine US manufacturers producing guns that periodically NEED rivets and pins to be tightened!

The AK action is indeed remarkable, but it's pinned barrel-to-extension design is a production expedient, a result of wartime needs, and is not a good arms design feature.

John

[securitysix]

Are the CETME and G3 rifles not pinned and pressed?  IIRC, the barrel is pinned and pressed into the trunion which is then welded into the sheet metal receiver.  And those are chambered for 7.62x51mm NATO.

[John Traveler]

SecuritySix,

The HK series (G3, HK33, MP5, etc) weapons indeed use pressed and pinned barrels.  However, I stand by my statement that pressed and pinned barrels are production expediencies, and normally not good design features.

Now, don't you HK fans (I am one too) get excited, but the HK design is indeed a "throwaway" assault rifle.  It's an excellent one, and uses remarkable high tech fabrication techniques including advanced steel pressings, CNC precision machining, hammer-forged barrels, CNC lathes, etc to create a durable design that holds up to 7.62 NATO ammunition.

The pressed and pinned barrel is not intended to be removed and replaced.  It's a one-time installation.  You can bet that the roller lock mechanism and the barrel extension it locks into are high quality steel and precision machined.  The pinned barrel and spot welds merely hold the barrel into the pressed receiver housing, and take no stress.  All the firing stresses are in the barrel extension and the roller-lock.

This is basically the premier post WWII assault rifle design that can get away with using pressed-and-pinned barrel assembly because of the precision manufacturing techniques available.  It is also a production expedient, cheaper than machining and assembling receiver and barrel with a threaded joint.

The original question was could the Moisin-Nagant rifle be safely fitted  with a .45-70 barrel pressed and pinned in place.  The answer is still NO!"
 
John

[BattleRifleG3]

Ok, so keep the threads on the Mosin...  anyone know where one would get a barrel so threaded, or what the thread specs are in case I could reproduce them?

[Larry Gibson]

BattleRifleG3

"I've wanted a 45-70 bolt gun that has decent capacity (ie 4-5, not 2 like the Gibbs SMLE conversions) and figured maybe the Mosin Nagant is the best choice due to its magazine interruptor and bolt face."

I have tried any 45-70 ammo in the MN as I have a Siamese Mauser 45-70.  However I have several MNs and I don't believe the 45-70 cartridge will fit into the MN magazine.  Will check when I get home.

Larry Gibson

[freddogs]

What about a 375 Winchester? It's mild and throws a bigger chunk of lead.

[BattleRifleG3]

Only prob there is that the rim of the 375 Win is significantly smaller than the 7.62x54, whereas the 45-70 is a little wider so the bolt can be adapted.  I'll try sticking a 45-70 in my Mosin mag to see if it fits.

[His lordship.]

John Travelor...I recall seeing some SKS rifles, Chinese as I recall, using pinned in barrels in the late 80's and early 90's.  They were sold as new, and I waited, until I could get a threaded barrel arrangement in 1993 at a price and appearance that interested me when I bought mine.  Otherwise the pinned-in barrel on the SKS variants must be rare as I have not seen many to date.  I wonder why they had some pinned in, and most threaded in?  :?

[John Traveler]

Hearing of pinned-in SKS barrels surprises me too.  I've never seen one.

The Communist Chinese use production methods and equipment set up by the Soviets when they were buddies (China kicked them out in 1960).  Almost all of their small arms designs and factories were set up on Russian made equipment.

[freddogs]

I'm getting curious. Did anyone try the 45/70 round in a MN magazine? Would the JDJ rounds fit a MN bolt face. Maybe I need to get the measuring equipment out and consult a gunsmith about taking barrels off. This certainly sounds like an interesting project.  :-D

[BattleRifleG3]

I have a 91/30 Mosin and borrowed a 45-70 round from a friend.  I'll try it in the mag when I get home in  acouple days.