45/70 Mauser


March 12, 2003, 10:28 PM
Before I begin, this question was posted on George's forum. So if it familiar George. It is.

I have been kicking around the idea of a scout rifle in 45/70 built on a Mauser action. I have built a number of rimless cartridge rifles on Musers, but never a rimmed. I have a few questions that I would like to put out for comment.

1) is this idea do-able?

2) How would one slot the back of the barrel for the extractor claw. WOuld this be done similar to the extractor notch found on WInchester rifles?

3) The base of the 45/70 rim measures .620 in diameter for a radius of .310". A Mauser magnum bolt face has radius of .269" from firing pin hole to bolt face rim, +/- .004". Turning the bolt face rim for the 45/70 case would leave precious little material left to hold the cartridge straight. Does anyone know how much would be too little?

4) I am assuming the 45/70 headspaces on the case mouth. Again, I have never cut a chamber for a straight walled case. The case rim should sit flat at the breach when properly reamed? We will worry about the chamber throat if I get that far.

Like I said, this is just an idea that i have been kicking around. But your input would be appreciated. Thanks.

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Jim Watson
March 12, 2003, 11:29 PM
I am not a gunsmith but I will get the ball rolling until one comes along.
1,2,3 There were a lot of .45-70s built on Siamese Mauser actions which were originally made for an 8mm rimmed round. They had rimmed case extractors and the slanted magazine box needed to get rimmed rounds to feed well in the Mauser design. The supply of those has about dried up. I haven't a clue as to whether you could modify a regular Mauser to handle it.

4. No.
The .45-70 headspaces on the rim. Standard ammo is heavily crimped to prevent bullet setback in a tube magazine, there is little if any casemouth to headspace on.

Gibbs is now hacking up No 4s for .45-70 so that is possible.
How about a .450 Marlin or a .458 American? Seems easier to get a bolt action to run with a belted case than rimmed.

March 12, 2003, 11:59 PM
IMHO, 4570 bolt rifles have feeding problems


March 14, 2003, 11:31 AM
I just built a 45/70 on a 91/30 Mosin Nagant action, even though I have many surplus Mausers sitting in storage waiting to be converted to something.

The surplus Mausers around right now are not good candidates for 45/70. The rim is just too big at .6".

I have no plans to get the magazine feeding 45/70.
I am going to shoot it single shot, if the winds die down, I will go to the range:)

September 30, 2008, 01:00 AM
sorry for bringing up an ancient thread. But I would like to know more about the Mosin Nagant in 45/70. What all did you have to do for the conversion?

October 6, 2008, 10:04 AM
Me too - bump!

October 6, 2008, 10:45 PM
i think a 450 marlin would be a better choice than a 45-70. to fit the 45-70's rim in the mosin's bolt head it would leave about .020 left in the outer ring. while the 450 has a smaller .532 dia rim. 450 brass & ammo is harder to find localy but its easy to find on the web.
the 450 will work with the mosins bolt head, ejector & extractor as is but i would still recomend soldering the correct size bushing to the bolt face to fit the 450's case.
the 450 is also a good choice for mausers if you don't want to go with the 458wm & it will feed with the standard magnum bolt & rail mods

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