Siamese Mauser 45-70 issues

[Blood Trail]

After about three years of searching, I found a Siamese Mauser converted to 45-70. Shoots like a dream at 100 yards with my reloads (jacketed bullets). Problem is, the chamber is a little oversized and it bulges my brass. Does Starline the worse.

I was thinking of putting a new Shaw barrel on it. I heard I can have the current barrel “set back”.

Should I have the barrel set back, get a new barrel, or leave it be?

If I leave it be, will I be able to load to Ruger #1 pressures with the bulging issue?

Here’s a 100 yard group using 300 grain Barnes TTSX and 300 grain Hornady HP.

https://uploads.tapatalk-cdn.com/20240108/045b8bd06682988db8ef8d10cf0bd8a1.jpg


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[Blood Trail]

Trying to upload brass….


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[Blood Trail]

https://uploads.tapatalk-cdn.com/20240108/d71ac2789a9f8c6ac708f0fff7d888a2.jpg


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[Blood Trail]

321892

[lancem]

If it were me and I had someone good enough to do it I'd probably set it back since it is a good barrel just needs rechambered.

[elmacgyver0]

If it were me and I had someone good enough to do it I'd probably set it back since it is a good barrel just needs rechambered.

Sounds like a plan.
Or can you reload the brass, just neck sizing?
As long as you're not going to shoot it in another gun, why mess with it?

[Rattlesnake Charlie]

If it were me and I had someone good enough to do it I'd probably set it back since it is a good barrel just needs rechambered.

Seems like the way to go. That barrel shoots good.

[Blood Trail]

Sounds like a plan.
Or can you reload the brass, just neck sizing?
As long as you're not going to shoot it in another gun, why mess with it?

BecauseI have two other 45-70’s I load for.


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[elmacgyver0]

Be sure I have two other 45-70’s I load for.


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Course you do, what was I thinking?
I have four .45-70s myself.

[725]

my first instinct was to say, "have it set back!" as is, it's tough on brass and who knows when that may lead to a case rupture. if I were to shoot it at game only and not enjoy it as a shooter, I'd toss the brass and live with loosing 5 - 10 cases a year. it really depends on what you want from it.
me - ? I'd save that fine barrel and have it set back - rechamber - and shoot the dickens out of it. good luck.

[Slugster]

I would set the barrel back about one turn and rechamber. Nice rifle! Congratulations.

[marlinman93]

Might get even more help if you hadn't posted this in the "Vintage Scopes" section.

[HumptyDumpty]

Might get even more help if you hadn't posted this in the "Vintage Scopes" section.
Well, this is within the scope of vintage....

[M-Tecs]

The 45-70 only has about .023" body taper. You need to take some accurate measurements to determine the how much you will need to set the barrel back.

[Blood Trail]

Might get even more help if you hadn't posted this in the "Vintage Scopes" section.

I read Vintage “Rifle” and Range Scopes.

Got it. [emoji1474]

Scopes vintage though.


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[Blood Trail]

The 45-70 only has about .023" body taper. You need to take some accurate measurements to determine the how much you will need to set the barrel back.

I’ll get my smith to handle that.


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[WILCO]

Nice looking rifle.

[Ben]

Set the barrel back and rechamber.

[TNsailorman]

I'd set the barrel back and re-chamber as you have plenty of barrel length and it would be cheaper and just as good as a new barrel. james

[PHyrbird]

I too like siamese in 4570.. 2" groups at 100y with just about anything U can feed & see with Iron sights... More comfortable than Marlins by far....

[marlinman93]

Well, this is within the scope of vintage....

The new thread area is for vintage scopes, rifle or spotting scopes.

[HumptyDumpty]

The new thread area is for vintage scopes, rifle or spotting scopes.

Just a failed attempt at a little word play on my part, perhaps I should have used purple font.

[405grain]

That case looks like the chamber was cut with a Morse taper reamer. With that much case expansion just ahead of the cartridge head you'd be risking a case head separation from over-working the brass in that region if you resized the brass a few times. Your gunsmith is going to need to evaluate the possibility of setting the barrel back. With that much case expansion the barrel will probably need to be set back more than just one thread. There's usually (but not always) a relief cut between the threaded shank and the shoulder of the barrel. If the barrel needs to be set back too far, and there's a relief cut, there might not be enough threads left on the shank for it to be used safely. If that's the case your gunsmith might have to cut off the shank and turn & thread a new one on the back of the barrel. This would depend on if there's enough meat on the breech end of the barrel to do this.

Though it's technically "tapered", a 45-70 is a straight walled case. Unless you make up a custom die for it, "neck sizing" is out of the question. To "neck size" a 45-70 case you'd have to full length resize it. This is not a good idea because of the possibility of creating a case head separation as stated above. Also, rechambering to 45-90 will not clean up this bulge because both cases have the same size case head. Your best solution to this problem is to set the barrel back and re-chamber. Your gunsmith will have to decide if that's possible. If it isn't, then a new barrel would be your second choice.