Would like to ask about the best method to alter a Siamese Mauser bolt face to accept a smaller rimmed cartridge...in the 7x 57r rim sizes, or possibly 303 Brit. The exact cartridge has not been decided on, but would like to gather info before deciding if this rifle project is something that I want to do. Would it be better to use a 98 bolt and alter it to fit the Siamese mauser action? Or have a custom bolt made? I'm new to this sort of project so please excuse my ignorance on this subject. I did search thru past postings on this subject but not much could be found regarding the Siamese Mauser bolt face. Any and all help would be appreciated. Thank you in advance.

I take it you have not priced a new hand made bolt lately.
Here is my question; WHY? The Siamese is not ideal for small cases; it's forte is large bore, and at least large rimmed ammo.
Best platform to use is a 7.62 Russian case; very close to the Siamese and it is 1000 times easier to open up the bolt face than close it up. Open up only .010 or so.
The 7.62 case is readily available, as are a number of cartridges small and large. I would go with a 405 Grenadier, There are others.

Are there actually some Siamese Mausers out there that HAVEN'T, been rebarreled to 45-70 yet? Every pumpkin chunkin, bear plunkin, muskrat sunkin Hillbilly in Alberta wants one of those damned things to play with !

What's even worse is that, they're all cheap skates and detonation flakes and they load those cheap 230 grain, hollow point pistol bullets in them to the point where they are almost flying apart. They rattle a bit going down the bore but they always seem to find an acceptable load that will kill gophers and get them a membership into the red mist society !

quote:

Originally posted by speerchucker30x378:
Are there actually some Siamese Mausers out there that HAVEN'T, been rebarreled to 45-70 yet?

They are all over the place in the states. It's not unusual to see one or two at a gun show and GB nearly always has some up for sale.

Check the Marlin .338 Express case; it's almost an exact duplicate of the original Siamese cartridge. I am building a Siamese Mauser for this cartridge and I'm sure that it could easily be necked up or down depending on your desires. No change in bold face necessary.

The 7.62x54R is also very close to both the 8x50R and 8x52R Siamese cartridges and the Russian brass is guaranteed to be around for the rest of our lives. How long will the .338 Marlin be around? It's already esoteric and Marlin isn't even making rifles for it anymore.

If you find the earlier model Siamese, the one in 8x50R, then you should be able to hit it with a 7.62x54R chamber reamer (figuratively) and shoot 8 mm bullets out of 7.62x54R cases with the necks opened to 8mm, an 8x54R if you will. You cannot do it with the later rifles chambered in 8x52R because that case is slightly larger in diameter than the 7.62x54R case.

I have tried 7.62x54R cases/cartridges in bolts of both 8x50R Siamese and 8x52R Siamese mausers and they fit beautifully without alteration.

I'm not criticizing your idea of building a .338 Marlin on a Siamese action, Russ. There are definite advantages for chambering for any factory round and .338 Marlin Ex is a good choice for a .338 caliber. But for any caliber that will fit the unaltered bolt that isn't 7.62 or .338 the cartridge must surely be a wildcat and I am just suggesting a better case for the wildcatting.

So I appreciate all of the replys so far but no one has stated what my best course of action is in regards to the original questions relating to a 7x57r case or a 303 Brit. in the Siamese. As an aside, I am aware of the 7.62 x 54r case option (have one already) the 45-70 option (dont want one) the .348-35 option (got one already). And now, coming full circle and in regards to altering the bolt face...or a new bolt option...I will ask the experts what the best option is for my preferred case(s). Please re-read the original post/question. And WHO would the gallery recommend to do the work? Thank you all in advance!

I have one in 30-40 Krag. I think it was pretty much a re-barrel.

Welcome to the forum sauercollector
Not sure why the experts won't give you a straight answer but you get what you pay for around here.
So if your Siamese bolt face is less than a 7.62 Russian by .010 as stated by one of the experts, then it is .550, a .303 Brit is .540 and as Craigster stated his project the 30/40 Krag is .545.
I'm no gunsmith but what you might try is partially feeding it a .303 and see how it takes the rim, if it will pick it up, and eject it from a partial bolt cycle.
My guess is you may have what you need however if you want it perfect then you need to find someone to take your existing bolt build up the face around the perimeter then mill the new bolt face at 303 Brit dimensions which I believe are .540.
I don't know anyone doing this work and by the sounds of the help on this forum none of these guys are going to help.
Good luck on your project it sounds interesting.

I have seen 98 Mausers which have had the rim of the bolt TIG welded up and recut for smaller cartridges. I have never attempted to do it myself. Probably because in 35 years no one has ever asked me to do it. But I assume the lugs were simply packed in wet toilet paper or other heat sink and then welded carefully to preserve the hardness. Even better would be to have it welded, then re-machined and then send it off to Blanchards or Pacific Metallurgical for annealing and re-hardening. I would imagine that any of the cowboys out there who are welding on square bridges and the like, could do it with little difficulty. I would expect that the welding and recutting would cost you $150 to $200. Re-hardening would probably be $150 to $200 by the time you figure in shipping. Getting it to feed reliably is a whole other matter. Like Tom was pointing out, it's a lot of money invested in a Siamese Mauser. But it is what it is.

I built my 45-70 on a Siamese back in 1990. I only shoot hard cast bullets and it is a hammer on whitetail. Frank Marshall load of 2400 behind a 300 Gr. bullet. One of my favorite deer rifles.

Look Mr Sauer; we are trying to help you; you are the one who said that the exact cartridge had not been decided upon and you were gathering info; you are getting exactly what you asked for; INFO. You did not say that those two cases were your preferred ones, so no reason to complain when you got better ideas.
I was giving you some better options than altering a bolt face smaller.
If you limit yourself to your two cases mentioned, then you are buying a lot of work, and expense. Here are the numbers;
7mm rimmed; .516
.303; .526
30-40 .535
Russian .567
A 303 will feed fairly well, they are sloppy in the magazine, will extract, but not eject because the small rims fall off the extractor. before it gets to the ejector.
The 30-40 works better in my stock Siamese. I recommend that.
Your best bet is still to go with the 30-40, or the Russian, both of which I can install for you.
You can't fit a 98 bolt; they are too long.
Welding up, or even soldering a ring on, a bolt face is a lot of work, and will cost hundreds of $. I am just offering better, more cost effective options. (My opinion).

Good info dcpd but you left one out:

8x50R/8x52R Siamese - .561"

Ok, one demerit for me. I was in a hurry.

quote:

Originally posted by Grenadier:
Good info dcpd but you left one out:

8x50R/8x52R Siamese - .561"

I've seen refs showing .550" and .556".

Original military contract drawings show the case rim specification as:

L 14.05mm (.553" minimum)
H 14.30mm (.563" maximum)

Bolt faces would have been made large enough to accommodate the largest allowable case rim plus a little extra.

Most civilian case depictions show a rim of .561".

Two demerets for everybody.

Nobody has thought about the extractors which are scarcer than the goose that laid the golden egg.

That said, the OP would be better off to find someone WHO would weld up the edge of the bolt face and extractor hook. The REAL issue here is as this steel in not a normal Mauser type steel but some other alloy and that makes the welding rather hard to do.

Much like shooting in the dark at a noise.

Just my 2 cents.

J Wisner

I agree with Jim about welding the bolt. I've soldered a "ring" on M-70 Hornets that had been opened to 223.

As I see it, there's very little stress, just holds the case centered in the bolt. At any rate, the two I've done have served years without mishap

I'd probably do a "look see" if the extractor can be modified by silver soldering a part or addition. Getting "spring" back in the part? Well..that would take thought and pre planning

Back to my original suggestion; leave the bolt face alone.
They were made in Japan using steel that seems similar to Arasaka steel; very tough stuff. I have opened up the bolt faces by grinding; a carbide bit bounces off.

I have never done one, but welding the bolt nose should be a breeze. Any low carbon rod should work well with a TIG and it's a non structural, non wearing area so the only critical part is maintaining whatever hardness it has with a heat sink. Welding those silly Mauser claw extractors is a hit an miss sort of thing. I have welded up countless numbers of those over the years. I usually lay a small bead of music wire on them with the TIG and then reshape and polish without rehardening. The weld tends to self harden to about 40Rc because the small area cools so quickly. I used to have about a 5% failure rate welding on extractors. More often than not they simply break at the weld joint.

It's till NOT, a cheap job.

quote:

Originally posted by J Wisner:
Two demerets for everybody.

Nobody has thought about the extractors which are scarcer than the goose that laid the golden egg.

That said, the OP would be better off to find someone WHO would weld up the edge of the bolt face and extractor hook. The REAL issue here is as this steel in not a normal Mauser type steel but some other alloy and that makes the welding rather hard to do.

Much like shooting in the dark at a noise.

Just my 2 cents.

J Wisner

Learned that the hard way. I don't know what they are made out of but I chased pores for weeks. I would never weld on a Siamese again.
Don