Siamese Mauser Conversion to .45-70

[FenderBender]

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.

Thanks,
Ben

 

[Vaarok]

You will likely have feeding issues with the box-magazine, as the .45-70 has a quite different taper than the 8x52R Siamese, even after the action is altered.

 

[MMCSRET]

Magazine alteration is standard procedure on this customization, at least in my experience. Was this rifle one of the older 8x50R converted to 8x52R?

 

[FenderBender]

MMCSRET,

I guess I am not sure whether it is a 8x50R or 8x52R. It is a M98 siamese mauser with mud cover and has the chrysanthemum crest and some siamese? symbols stamped on it. I would guess it has never been converted to 8x52R. Is there a way to tell by looking at it?

Ben

 

[oneshooter]

Built one a few years ago from a barreled action. Still have some feed problems , but the rifle shoots like a champ! Prefers a 400gr sp with a HEALTHY dose of IMR 3031 behind it!!

Oneshooter
Livin in Texas

 

[Jim Watson]

You will need a scope safety.

As I recall, if it was converted to 8x52R they would have cut down the tangent rear sight track for the flatter trajectory of the later round. Look at the Siamese graduations down the side of the sight base. If they are cut in half, the sight was altered and presumably the chamber was altered.

If this is an unaltered original good condition military rifle, somebody will be along to give you a hard time about Bubbafying it. Me? I don't care, it's not mine and I don't collect obsolete military surplus.

 

[NCsmitty]

Congratulations on deciding to do the conversion. I was just curious about your choice of a stock.

NCsmitty

 

[FenderBender]

Jim,

Thanks for the information. I have no problem with bubbafying this action. My purchase did not come with a stock, just an action with a corroded barrel. The action is in pretty good shape so it seemed like the perfect candidate for a .45-70.

NCsmitty,

I have not really thought much about the stock yet. Once I send it to ER Shaw for the conversion and new barrel they are quoting a 4 to 5 month turnaround time, leaving me with plenty of time to decide on a stock. I was thinking something walnut or maple but am totally open to suggestions.

 

[brentwal]

.450 Marlin may be a better conversion.

 

[Vaarok]

He said it was an action, I trusted he meant action. Nowadays most collectors are starting to worry less and less about the Siamese Mausers, simply because they've dried up and risen in price to the point it takes a lot of willful ignorance for someone to chop one.

 

[dirtyjim]

i wouldn't have the bolt handle forged i would have it cut off & a new handle welded on. costs about the same. great american gunstocks had a nice stock for a siamese in their bargain section

 

[MMCSRET]

My mistake, I did not read "action". I was thinking rifle, as I understand it was simply rechambering and recalibrating the sights when it became 8x52R. No problem at all in my limited experience.

 

[FenderBender]

What is meant by a scope safety?

If I am looking at a 20" or 22" barrel what would be the recommended twist?

Thanks

 

[MMCSRET]

Twist will depend on the bullet type you choose: lead, jacketed, light, heavy? Talk to your barrel maker.

 

[Jim Watson]

"What is meant by a scope safety?

Look at your action. The Mauser wing safety swings 180 degrees at the top of the bolt sleeve. It will hit the objective bell of a normally mounted scope sight. There are three ways I know to get a safety to work under a scope. One replaces the wing safety with a lever that moves up and down over about a 40 degree arc on one side and does not have to move past the scope. The next is a safety that swings through a horizontal arc on the right side of the bolt sleeve like a Model 70 Winchester. Or you can use an adjustable trigger with its own safety and ignore the wing safety, or take it off and plug the hole.

There are Bubbamounts that put the scope so high the safety will swing under it. Or you can use a Scout scope mounted way forward out of the way. But to do it right you will use one of the systems above.

"If I am looking at a 20" or 22" barrel what would be the recommended twist?

Rifling twist is overemphasized and overstudied these days. Nearly all current .45-70s have 18" twist barrels to be sure to handle the heavy bullets. Unfortunately, Shaw only lists a 14" twist which is really meant for the .458 Win Mag or a 22" twist which is the original Trapdoor Springfield standard.
If you mean to magnumzize your Thai with a steady diet of 500 grain jacketed bullets at top loads, get the 14.
If you will be happy with real .45-70s loaded with 405 jacketed or cast and no more than 500 gr cast, get the 22, it worked then, it will work now.

 

[FenderBender]

Received my .45-70 barreled action today

I received my barreled action from ER Shaw today and just wanted to share some pics with THR.

Below is what I had done to the Siamese Mauser action:

Alter Siamese Mauser action for .45-70 cal.
True bolt face
True face of receiver
Lap locking lugs
Forge and polish bolt handle for scope
Drill and tap action for one piece Leupold mount
Supply and install Sportsman Timney Trigger
Supply and install Timney Low Safety
4140 20” barrel, 1 in 22” twist, # 3.5 contour
Fit and testfire barrel to action
Premium blued bead blast matte finish of rebarreled action

Not done yet as I still need to decide on a stock and the optics, but am getting pretty anxious to try it out!

Ben

 

[Maverick223]

Aw, forget about the stock and fire it a couple times, I have done it scores of times with my .22lr out of the stock. Looks purdy.

 

[jpdriver1]

I acquired one of these several yrs ago --- shoots 200-250 yds very well w/o scope, just the iron sites --- I've used 300 gr for lg deer and 405 for elk in No Idaho

 

[alemonkey]

Wow, I'm jealous. That's going to be a really cool gun.

 

[FenderBender]

Thanks for the compliments.

Are there any other siamese mauser stock manufacturers in addition to Richards Microfit Gunstocks?

Thanks,

Ben

 

[Ripple]

Can anybody give me the appropriate scope bases for the Siamese Mauser? I have some Redfield 98 Mauser mounts, but the contour of the rear receiver ring is wrong. Any help? Need brand & base #.

 

[MMCSRET]

It's just possible that you may have to buy a base blank and have a machinist fit it to your action. I'm surprised that Shaw didn't annotate which base they used for the contour. I'd call them with the job # and see what their work order said they did, it's just possible they have it in their finishing notes.