Rebarreling a siamese mauser?

[Gdbyrd]

I have an old 1970ish Navy Arms converted siamese mauser. It's chambered in 45/70. The rifling on it is pretty well worn, it's also never really grouped very well(only used factory ammo).

I'm considering rebarreling it so I can get some good use out of the action. Would this negatively affect the value at all? I'm not sure how that works since it's definitely not original.

 

[Float Pilot]

No. There is no collector value.
Back in the 70s I helped pay for college by working at a gunsmith shop. We did LOTS of 45-70 conversions on the Siamese Mauser actions. They are very strong and can be loaded to 458 mag type velocities. The only hold-back being the strength of available 45-70 brass.
Due to the magazine design, you need to re-barrel it to another rimmed cartridge. With a rim diameter size similar to the 45-70.

Are you sure your poor groups are not due to bad action bedding or a bad pressure point in the barrel channel?

 

[Gdbyrd]

In all honesty I am not sure. I just know I shot a few groups with it and wasn't at all impressed with it, then decided to check the barrel a little closer. The rifling is pretty much smooth. It's barely raised at all, I'd be hard pressed to measure it...could this be normal? The action/stock are in excellent shape so it seems unlikely that the gun has been shot a lot.

I am considering getting into casting and using this rifle as my first project with that in mind. If I remember correctly it was grouping 2-3" at about 30 yards I think(5 shot groups). All I shot were the 300ish grn remington factory offerings. I did the shooting over the summer and put the gun away..just now looking into it again since I want to get into casting and there's a lot of offerings for the 45-70, plus this gun is one of my rougher ones.

 

[Freedom_fighter_in_IL]

2-3" at 30 yards? I get better grouping than that with a smooth bore shotgun with rifled slugs. I would have to guess there is something way off on that rifle. And it is very rare to have a shot out barrel on a 45/70. I've seen them after 1000's of rounds shot through them and the rifling still fairly clean and crisp. Have you made sure to remove all copper or lead fouling? Maybe the person that had it before you shot cast bullets and didn't clean it up as well as they should. Get you some of that "wipe out" foam. I would also check the bedding as well.

 

[Float Pilot]

Sounds like new barrel time. Fortunately you live in the Republic of Texas so finding an honest gunsmith should not be all that hard.
Threaded shank diameter of .515" long, .990" in diameter, with 14 threads per inch.

Just order a barrel blank from the barrel maker of your choice. Think about what twist rate to order if you want to shoot heavier cast bullets.

 

[NCsmitty]

It's hard to believe, but I guess not impossible, that a 45-70 would wear out a barrel like that. That would be a lot of rounds and/or a poor quality barrel.
It certainly is worth a decent barrel if that is the course of action taken, as that strong (Nippon) Siamese action really can make the 45-70 a heavy thumper.



NCsmitty

 

[Float Pilot]

The 1903 Siamese Mausers, (Siam = Modern Thailand) originally took a 8x52mm Rimmed cartridge (181 grain bullet) that was only ever used in that rifle. Some sources claim that they were license built in Thailand, but most folks say that they were made under contract in Japan and have the three interlocking rings as the Japanese proof mark.
Whatever you do, try to save the stock. That action is not exactly the same as any other Mauser action. 40 years ago they made lots of stocks for sporterizing them. But today you won't be able to find jack-squat.

 

[CnRnut]

They started life as 8x50R,then were changed over to 8x52R

 

[Curator]

Chances are your accuracy problem was the ammo. It would be difficult to wear out a new barrel with Remington 300 grain .45-70 factory ammo. Those bullets are purposly made soft to shoot in the old Springfield trapdoor rifles. It probably needs a good cleaning and some quality reloads to shoot well.