416WSM on Siamese Mauser & 416/348Ackley Improved on Martini

[BlueFlyer]

This all began about 30 yrs ago when I acquired 3 large Martini actions in various states of disassembly. I managed to salvage 2 working actions out of it. Back then I barreled one of the actions to 45/70. This is one of my favourite rifles, it points like a shotgun and with its 22" barrel is a very short and handy rifle. It weighs 61/2lbs so with 400gr Remington projectiles doing 2,000fps you know when you pull the trigger.
Recently I thought it was time to rebirth the second Martini action. I happened to have a new 416Taylor barrel, but the shank thread was wrong and the Taylor is too long for a Martini not to mention the pressure. In Wolfe publishing "BIG BORE Rifles and Cartridges" there is an article on the 416/348Improved. This was my choice, and then I placed an order with Pacific Tool & Die and waited.
As I was waiting for the reamers to arrive ( I ordered a finisher and resizer plus go gauge) I was browsing articles about 450 and 500Alaskan on Siamese Mausers which sparked some interest in that action. I also came across the 325WSM case dimensions and realised that by using the WSM case I would have a rimless version of the 416/348AI that I was making on the Martini. A couple more clicks and I found a bare Siamese Mauser action for not much money, but there was a sting in the tail. The first issue was that the action arrived without an extractor, then the Firearms Registery would not release the action to me, it had to go to a registered gunsmith to fit the barrel.
Long story short, the reamers arrived and I purchased 416 barrel from Sprinter Arms, the barrel has been fitted to the Siamese Mauser and chambered for 416WSM using the 416/348Ackley Improved reamer. It also now has an extractor, that I have no idea as to its true origin. My Gunsmith had a draw with various extractors and there was 1 that looked like with a little modification it would. A few minutes with the die grinder and it fitted the bolt.
I picked up the barreled action today and will post some more photos on the weekend.

 

[skydiver386]

The Siamese Mauser is quite strong, and should work well for this conversion. How much of the other work will you be able to do yourself?

 

[BlueFlyer]

Hi Skydiver
I am planning on doing all the remaining work. I have done the bolt handles both my Enfields (P14 & P17) and Mauser 93. I want to try making a 2 position safety, hopefully a doner K98 bolt shield will fit the Siamese bolt. Hinge the floor plate and all the barrel fittings. Then the stock out of local timber, Tasmanian Blackwood. This will all take some time.

 

[Boyd Brooks]

A couple of true oddities, but I love it. I find a lot of range time, turns into story time, and watching someone else try my less than mainstream rifles, than practice time.

 

[AZDAVE]

The 348/416 is an interesting project. Looking forward to seeing what kinda performance you get out of it.
the 416 WSM on the siamese action will be fine, that is a very strong action.

 

[Ontario Hunter]

Are those Siamese Mausers single stack? Its angled magazine is designed for rimmed cartridges. Wondering if that presents issues for rimless? Probably not.

 

[skydiver386]

I would think the main issues to be the bolt face and the extractor. The feed lips might take some fine tuning also.

 

[Ontario Hunter]

I would think the main issues to be the bolt face and the extractor. The feed lips might take some fine tuning also.

If it's an 8mm rimmed version of the Siamese Mauser then it would require changing a 16mm bolt face and extractor into a 13.6mm WSM ... if that's even possible. But apparently some Siamese Mausers were made in 30-06 and even 30 carbine (ugh!). If one of those, then it would be a manageable build to open the bolt face and extractor. But can they be reduced in diameter? And you're probably correct about feed lips. The feeding rails for a fat rimmed single stack cartridge would have to be widened for a narrower cartridge = adding metal. Would seem to be a challenge.

 

[BlueFlyer]

If it's an 8mm rimmed version of the Siamese Mauser then it would require changing a 16mm bolt face and extractor into a 13.6mm WSM

The Siamese 8X50R had a rim diameter of 14.12mm and the WSM is 13.6mm, Below are some photos of the Siamese bolt along side my P14 that is in 9.3X64B. I have included some close ups of the markings on the extractor - I suspect it was for some form of rimmed cartridge as it had an extreme ramp. If anyone can identify the markings that would be great. Siamese Mauser on the left.

 

[mauserhunter]

I've thought about doing a 375/348ai to go along with my 45-70 Siamese but really don't need it since I mosly just hunt deer. Always thought a 7.62x54r would fit nice in them the original mag is just over 3" would have been nice and cheap to shoot but now not so much. Seems like a waste not building a Siamese into a larger round but 303b or 30-40 krag would be fun. My dad had one in 450 Alaskan and reamed one out to 8mm-348ai.

 

[BlueFlyer]

Equally most of my hunting is Sambar deer, but really, this is not about logic, its about the passion of trying something. I don't need both a 416WSM and a 416/348AI, but I can. At least with the Martini I don't have to worry about feed issues. If I have 3 cartridges in my forehand, I am almost if not equally as quick in reloading the Martini as any bolt action. And the Martini will point like a shotgun.

 

[Ontario Hunter]

The Siamese 8X50R had a rim diameter of 14.12mm and the WSM is 13.6mm, Below are some photos of the Siamese bolt along side my P14 that is in 9.3X64B. I have included some close ups of the markings on the extractor - I suspect it was for some form of rimmed cartridge as it had an extreme ramp. If anyone can identify the markings that would be great. Siamese Mauser on the left.View attachment 616572
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The concern I would have is will the sloppy bolt face hold a rimless WSM cartridge firmly enough to extract AND eject it? I'll have to look at Duane Weibe's book again but I seem to recall he said to only open bolt face two thousandths above spec to accommodate irregularities in different manufacturers of brass.

Push a WSM brass under the extractor and try to close the chamber. If it won't close, cut down the case till it will. Then try to extract/eject. Even if it does, you've still got the feeding rail issues to sort out. How do you make the rails grow for a narrower rimmed cartridge. Again I ask, is the Siamese action single stack magazine (one cartridge exactly above the other) or are cartridges staggered? If single stacked, it MIGHT be possible to cut the feeding rails back for staggered WSM cartridges, but then the magazine box would need to be widened per Paul Mauser's cosine 30 degree formula. If Siamese magazine is staggered, I don't think it is doable. Not without some expert building up the rails with tig weld and remachining. Others have attempted that for botched big bore builds on standard 98 Mausers but with very little success. Very expensive failures! And finally, you'd be looking at serious modification to the follower. Siamese magazine and follower is designed to push up rimmed cartridges. Note how the magazine is angled. This means the follower inside it is on an angle. But the WSM is almost straight and no rim. I doubt very much the Siamese follower would feed WSM properly.

Build this action into 45-70 or one of its wildcats. Find a standard Mauser donor action and build your WSM project. It will be much more doable. I built one into 404 Jeffery (essentially same rim as WSM), having never done anything like that before. I could help you with that project.

 

[BlueFlyer]

The Siamese Mauser is a typical Mauser 98 and has a stacked magazine.
Early days but with only 3 rounds in the magazine, if the bullets are seated down to the cannelure then the feed is not 100%. But when the bullets were seated out per the photo they feed without issue.
Extraction has not been an issue.
The real test is going to be loading, firing and extracting live rounds.

 

[BlueFlyer]

The logic behind why I thought the Siamese Mauser would be a suitable doner for a WSM based cartridge is that the rim diameter of the Siamese 8X50R is 0.555" and the base diameter of the WSM is 0.555" = identical. I did not believe I would have to touch the rear of the guide rails. The shoulder of the 8X50R is much smaller @ 0.450" compared to the WSM @ 0.538 and that is where I think there is an issue. The shoulder is being push too far acrosswhen the bullet is deeply seated and it slides upo the rails. With the bullet seated out, the tip of the projectile engages with the chamber before the rail can push it too far and it all works well. If anything I think I need to open out the front of the guide rails. But I am very very very reluctant to remove any metal from the guide rails at this point until I have experience loading and firing.

 

[BlueFlyer]

I did get some time this afternoon to start on a new bolt handle for the SM. I really like the modified bolt of my P17 & P14, as the knob is right out there and easy to grasp. Rather than just bend the existing one down I am going to weld on a new longer bolt handle. More work to do with polishing and removing all the machining marks, plus a small line of knurl around the knob.

 

[Ontario Hunter]

I think it's the bolt face you need to worry about. Both cases are overall about half inch thick ahead of rim with 8x50R being narrower. And narrower is workable. You want to go from thinner to fatter cases when modifying feeding rails. I tuned the rails of an 8mm Mauser to cycle 404 Jeffery ... and it cycles smooth as silk. But it required significant changes to the rail. I also had to deal with significant modification to loading ramp which this project would avoid. And magazine width would work (I had to buy 416 Rem bottom metal for my build). So I can see this build MIGHT be doable IF the bolt face will work. But you're looking at two hundredths difference, not two thousandths. And the difference is going the wrong way. Very difficult reducing the diameter of bolt face. It may be this bolt face as is will still extract and eject a WSM cartridge properly, but I seriously doubt it. That's a lot of slop. I think you'd be running the risk of cases stuck in the chamber or coming loose from the bolt face before ejected properly. Unfortunately, I didn't consider that WSM is rebated rim so my idea of cutting off a case and trying it for extraction is nonapplicable. You wouldn't be able to close on the cut off WSM case in the 8x50R chamber no matter how short you cut it: the WSM case is 0.050" thicker at head diameter. Sooo ... you won't know if you can actually make the 8x50R bolt face work with WSM cartridges until after you've bought and installed the WSM barrel. What do you do if it doesn't work? Ask around to other gunsmiths who have more experience with modifying bolt faces. I think most of them will wince at rebated rim. Making them feed is tricky to start with (a big problem when Taylor first introduced rebated rims in standard 98 Mausers) and you are dealing with a Siamese Mauser angled magazine and follower and follower spring. Rebated rims require more follower spring pressure on case head but with that magazine designed for rimmed cartridges you're looking at REDUCED spring pressure at case head.

 

[BlueFlyer]

Sooo ... you won't know if you can actually make the 8x50R bolt face work with WSM cartridges until after you've bought and installed the WSM barrel. What do you do if it doesn't work?

The 416WSM barrel is in the action, that is how I was able to check the feed function mentioned earlier.

 

[Ontario Hunter]

Sorry, I didn't understand the barrel was already attached. So how's it extracting/ejecting? I don't see the feeding rails being any big obstacle. From what I'm reading the historic problems with rebated rim that gained it a bad reputation early in development were feeding issues associated with follower and especially follower spring. Taylor was trying to squeeze more gas out of standard 98 Mauser action because of magnum action scarcity. Opening the bolt face to 404 was pushing the envelope (though some did open it to 416 Rigby) so he kept that rim and expanded the base of case = rebated rim. Feeding problems caused the concept to flop early, especially among dangerous game hunters who were the target market obviously. Eventually the feeding issues were overcome by somehow modifying the follower spring. Apparently, it involved a significant change. I would like to pop the floorplate on a Winchester Model 70 WSM and see what they did to the spring. Sounds like there might be two springs?

Given the history, perhaps you should look into the follower spring issue before moving ahead to feeding rails ... IF ejection and extraction are okay. Yes, maximum outside diameter of both cartridges is the same so you likely will only have to modify rails at the shoulder. Whether you'll need to change the mag box remains to be seen. But wait, you said it's single stack? Then that box should work. It should be wide enough even at the shoulder. When you start modifying the rails, have two cartridges in the box. Get the rails tuned for two cartridges (which should be the same for three in the box) and then proceed to tune the FOLLOWER (or follower spring?) for just one cartridge in the box. Don't touch the rails again. I modified a rail for each side individually to accommodate staggered rounds and then follower for last round in staggered magazine. If your box has cartridges stacked vertically, you will tune both rails at the same time for two in the box.

The slop in bolt face may cause some slight feeding issues. Cartridges will probably not be centered when pushed out of magazine onto the bolt face. The extractor claw will push the rim off center because the bolt face is larger diameter than rim. As the bolt is closed the rim will be forced into center alignment with bolt face by opposite case wall contacting chamber. Perhaps you can grind off enough of the claw to allow rims to center on bolt face. But be careful. The rule of thumb on modifying extractors for opened bolt faces is remove just enough of the claw so that a loaded cartridge will barely stay hooked on bolt face when bolt is removed. But you have a bolt face opened too far so that method does not apply. Not sure how you would determine what to remove from the claw. If it cycles rough and you see drag marks on the side of brass, maybe think about cutting back some on the claw ... keeping in mind, as you well know, extractors are not easy to find for that model.

It's an interesting project. I'm not sure I've heard of this being done before.

 

[BlueFlyer]

I would like to pop the floorplate on a Winchester Model 70 WSM and see what they did to the spring. Sounds like there might be two springs?

Can anyone help with a photo?

 

[BlueFlyer]

Below are a couple of photos of the feed rails and cartridges. I believe that I need a little more margin with the cartridge shoulder. At some point I thing the shoulder point on the feed rail and magazine needs to be moved forward - any feedback or opinions appreciated.

With the projectiles seated out, they feed, extract & eject.
Then I also found some time to weld on the new bolt handle. Predominately I use Arc welding and very small welds and plunge into a water quench to limit the heat migration. You can see the limited heat affected zone on the polished bolt. The bolt body was always cool to touch.

I used my tool & cutter grinder to grind down the scope clearance feature. The bolt is easily accessable.

More cleanup & polishing required at the weld point. I also ran a line of TIG on the inside of the root. TIG puts alot more heat into the bolt, but I still controlled it with a water quench.