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Siamese Mauser Conversion To .45-70

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#1 FenderBender

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Posted 15 August 2008 - 03:58 PM

I have recently purchased a Siamese Mauser action that I would like to send to ER Shaw for conversion to .45-70. Looking over their gunsmithing prices I have put together the list of services I believe I will need:

Alter Siamese Mauser actions for .45-70 cal.
Forge and polish bolt handle for scope
Drill and tap action for Leupold or Weaver bases
Premium polish and blue of action
Code 1 thru 5 barrel, finished, chambered and threaded for your action, 4140
Fit and testfire barrel to Bolt Actions

I am new to converting a Siamese Mauser action, am I leaving out any necessary or recommended services?
What would be the recommended barrel length, contour, and twist?
Would I be better off with a Leupold or Weaver scope?

Any information that you could provide would be greatlly appreciated.


#2 gun nutty

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Posted 15 August 2008 - 05:26 PM

I think the smallest barrel contour that Shaw offers for the 45/70 is #3 (a varmit contour).

Looking at the dimensions, the forward chamber shoulder sits 1/2" forward compared to standard sporter barrels.

I'd consider having them set the barrel back 1/2" for a more pleasing barrel profile.

You don't mention anything about twist. The .45 barrels come in either 1-20" or 1-14". The 1-20" is typical for slower 45/70 trapdoor velocities, and the 1-14" is more for the .458 Win. A souped-up 45/70 would sit somewhere in between. Oh, decisions, decisions...

Does it have to be a 45/70? De Haas specifies the Siamese as a good candidate for the .458 American (.458X2"). That would also make it an excellent candidate for the .450 Marlin.

If your action was already well blued, you could spend a little more and get a stainless barrel, and omit the barrel blueing. It would be a wash on cost, but stainless is nice.

Do you like the bolt handles they offer? If you want a beauty, have Z1r do a handle instead. The photos of his design are incredible. I'd spend the extra for a true, classic look. I'm talking the design with no sweep on it.

Barrel length... What are you using it for? At the range for cast bullets, 24 to 26 would be dandy. For a true "brush buster", 20 is much more manageable. Some folks split the diff with 22.

I think a Burris 4X Compact would be wonderful on a rig like that, provided you make it graceful enough with a classic stock and swept-back pistol grip. Low, two piece mounts, of course.

#3 FenderBender

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Posted 15 August 2008 - 10:30 PM

gun nutty,

That really is a wealth of information. I appreciate it.

What are the pros/cons between .45-70, .458 and .450?

Is Z1r a member on this board? *edit Nevermind I see that he is.

You definitely are right.
Decisions, decisions, decisions...


#4 BradD

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Posted 17 August 2008 - 02:13 PM

Ben, just one thought about cartridge. The usual reason that Siamese are made into 45-70 is because they are designed for a rimmed cartridge and 45-70 is rimmed. The Siamese are a little hard to find these days and they are the only 98 that works very well for rimmed ctgs.

The American and 450 M are belted and they work in anything. A souped up 45-70 is every bit the equal of either.

Go with the fast twist on this (14).

Sort of an imperfect general rule: the bigger the hole, the less length you need. Also 45-70 works well with faster powders like IMR4198, so you really don't need a long barrel. Those barrels get heavy! I have a 26" I love, but I sure get tired carrying it, I like my 24" much better in the bush or on a hillside. Go with 22-24". It'll be fine and your shoulder will be happier.

Good luck,

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