Does anyone have a file on this they could post or email? Or suggest a book that describes it in detail? I have heard that H&H opened them up both in the front AND in the back, I think 1/8" in both areas?

Not in any hurry, as I have decided to turn the action I was intending for this project into a 243 instead so I have time (like a year or two, at the rate I've been working on stuff!) but hey, it is a slow day today and too cold outside.

This conversion is not recommended as it weakens the 98 action. It's too easy to find H&H length actions to take a chance with a risky modification.

I am currently having a 1909 Arg. opened up to 375 H&H. The 98 is fully capable of dealing with the 375. Just look at all the early high end rifles in 375 built on 98's. There are several here who can answer your question much better than I can. I do know that to determine which way to open it up depends on which bottom metal you are using.

Good luck with your project.

I was planning on building the bottom metal too.

It is my understanding the 375 H&H was designed to fit into the standard 98 action. Granted, Kuhnhausen says don't do it but literally thousands of guns have been opened up. I'd just like to learn more before I do it! As I said, I have plenty of time as I put another project in front of this one but I was hoping someone might have a file on this they could post.

Mark,
as teh MARK-X/Interarms/CharlesDaly ETC are all 98 mased actions, yes, it can be done. In fact, if most of the metal is taken from the back of the action, it's just metal work, nothing to do with the strength of the action...

I would suggest to you a 376 steyr, which is about 10% of the work.... open the bolt face, "polish" the ramp/rails, and put at least 5 down... NO grinding, no mill, no cutting the rails.

If you want to do the 375 on a 98, get some junk turk actions to practice on...

jeffe

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Originally posted by Mark:
I was planning on building the bottom metal too.

It is my understanding the 375 H&H was designed to fit into the standard 98 action. Granted, Kuhnhausen says don't do it but literally thousands of guns have been opened up. I'd just like to learn more before I do it! As I said, I have plenty of time as I put another project in front of this one but I was hoping someone might have a file on this they could post.

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It can be done, BUT the .375 WAS NOT DESIGNED to fit into a standard 98. That's why there are Magnum Mausers!! Even a correctly -loaded .30/'06 is a tad too long to fit a standard 98 magazine box.

Roy Dunlap's "GUnsmithing" book describes the process. It is a good reference book for other oeprations as well. It was written a long time ago but it is still a good book.

THere is nothing worng with opening up a standard M98 Mauser if proerly done. No telling how many have been done this way. Hundreds of thousands, I am sure. I have never heard of even ONE doccumented case of a properly worked Mauser failing because it was opened up. In theory it is slightly weaker, But I have enver seen anyone do a Fintite Element Analysis of of e M98 and an opened up M98 to see just what happens. It would be a bear to model, but the results would be very, very intersting. ANy FEA experts on the board? ANy professors here with a research assistant that you can throw this on? I have never thought about it until now, but this would be very interesting to see.

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It is my understanding the 375 H&H was designed to fit into the standard 98 action.

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NO...absolutely not as ElDeguello said...NO.
That said it's possible to modify a fine '98 action to handle it and if you can do the work yourself get Dunlop's book and follow his instructions. It's not a job for a novice!!

If you're hiring the work done you'll be far better served by finding a commercial mauser already suited to the cartridge. Whitworth comes to mind.....

If you already have the mauser action and want a .375 performance level from it you should look at the 9.3 X 62 cartridge that requires a lot less work.
The .375 Taylor is also a fine option for the Mauser action.

Yes, it can be done. Harry Selby's famous .416 Rigby was built on a standard 98 action.

Personally, I'd rather not go this route. I'd rather error of the side of more materials in key areas of the action, and more room. I'd go with either aModel 70 Classic action or a modern commercial Mauser action of appropriate size for a .375 H&H.

AD

There's plenty of room in a standard length Mauser to open it up to 375 length cartridges. Aftermarket bottom metal from Sunny Hill or Blackburn makes the job easier, or you could find a Mark X or older commercial FN in 375. The Mark X and Sunny Hill require the metal be removed from the front of the action. I've been told but don't know for sure that Blackburn allows it to be taken from both ends.
Harry Selby, the famous Africa PH, had a 416Rigby on a standard length action, built by Rigby I believe. Now THAT'S openning up an action!

One of my gunsmithing books covers a conversion to 375 H&H. I'll have to try and find it.
The basics were to take the magazine box, cut the front out. Bend a pice of sheet metal to fit on the inside of the box and be spring loaded to hold in place. Put a loaded round in the box and adjust the new front for clearance and fit. Weld in place. Use this as a guide for opening up the bottom lug area. Put a round in the magazine and see where the bullet will ride up on the lug, then remove just this area. Check it from both sides removeing only from the middle until it feeds.
Others here have said that you can lap the front lugs until the rear lug comes into contact and this will help with the strength issue.
A 375 Dakota sounds like a reasonable alternative that would be standard length.

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A 375 Dakota sounds like a reasonable alternative that would be standard length.

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Good idea, although might require a wider magazine and rails. The 404 Dakota appeals to me too: a shortened blown out 404Jeff, similar to the 416Howell but larger 423 bullet.

Today when I think of a .375 H&H it's of a rifle set to travel for dangerous game. This means that it functions well and has CRF and a perfect safety along with the usual features such that this custom fits you. It might even have a drop box magazine for instance.

So if you do a home brewed .375 I would finish it even if you need help. As mentioned above if your going half way with it then some other cartridge would be a lot easier. It's that the .375 H&H is not perfect itself but it's all moved in and everything.

Think over what your finished Mauser would be like. Many .375's end up quite heavy. It would not be a bad thing to own a 9.3X62 in a rifle that weighed a little less and had a shorter barrel than how a proper .375 would be. Sort of a handy all around woods and yet a DGR rifle all rolled into one.

I have built .416 Taylors on standard 98 Mausers. I have to believe a .375 Taylor as mentioned before would be a far less labor intensive project and you will be within a gnat's eyelash in performance. The biggest challanges will be opening the bolt and the feed rails then getting the magazine to accomodate the extra round. So that you can have 3 down and one in the barrel. None of these things are particularly difficult work through.

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Originally posted by Mark:
Does anyone have a file on this they could post or email? Or suggest a book that describes it in detail? I have heard that H&H opened them up both in the front AND in the back, I think 1/8" in both areas?

Not in any hurry, as I have decided to turn the action I was intending for this project into a 243 instead so I have time (like a year or two, at the rate I've been working on stuff!) but hey, it is a slow day today and too cold outside.

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Mark
H&H did open up their M98 actions both in the front, in the back and in bothe sides. The sides can be opened up different much, H&H choose not to open them so much that the cartridges got into a optimal "cross", wich did get the consequence that they only accepted 4 cartridges, dispite the used a drop magazine, at least this is a fact on my own 30Super H&H rifle.
Above: Original H&H converion.

I have opened up another M98 myself and it is no problems to optimize it so it accepts 5 cartridges(with drop magazine and 4 with a modified std magazine).

Please let me know if there is any specific measures you need.

Martin

Martin thank you for your information.

Also thanks to Marc Stokeld, he has been most helpful.

I decided to get the information straight from the horses mouth as well, and contacted Holland & Holland. They answered my question in a day, so I would heartily recommend their service!

Anyway, here is what I received from them, verbatim:


The Mauser action M98 (model 1898) came about many years before the .375 in 1912. However it did not take us long to realize that the M98 could be adapted.

The only major problem is the length of the cartridge (the bolt face also needs opening up to accept the larger diameter of the .375 cartridge head- the M98 was primarily developed for teh German Infantry's 7,9/8x57 and many other countries in 7x57). Therefore the mag box has to be replaced and the aperture in teh base of teh action is lengthened by removing metal from the front.

Theory and common sense suggests that this is not such a good idea as this is actually removing metal from an area that supports the bolts locking lugs. This is true BUT such is the strength of the M98 that it can cope easily- viz the thousands of .375 H&H made rifles in extended use.

The so-called magnum mauser action is ideal. Mauser made a lengthened action for their own brand sporting rifles (hence the term "Commercial Mauser") which meant it was an expensive option to buy a mauser rifle (actions only did become available later) to rebuild into another calibre-- ex "Military Service" was much cheaper and as the .375 was our longest cartridge we were OK. However teh 350 Rigby and more famously the 416 Rigby are even longer and cannot be made to work in a M98 action; they do need a longer action. The 505 Gibbs is too fat and the 500 Jeffery is just OK.

One last thing, the appellation "Magnum Mauser" suggest greater strength- THIS IS NOT SO- it is only longer. The "magnum" bit originates from the type of cartridge that the action is associated with. In reality most sporting rifles operate within similar pressure bands.

So there is the answer straight from H&H, written as accurately as I can.

OK I'm going to soak my hands now, that was a lot of typing!