ATTN Mauser Experts, Need Help

[ACM]

I am looking at purchasing a pre-war large ring Mauser. It is an exceptional looking rifle built by JP Sauer & Sohn.
The rifle is chambered in 9.3x57 Mauser and I have a few questions:
1) The bore slugs .369” (.003” over bullet diameter) across the grooves. Will this hurt accuracy or possibly be a reason not to purchase?
My main goal is to ream the chamber to 9.3x62. I do not want to do the work involved if the bore is out of favorable tolerance.

2) The rifle has very nice claw mounts, with the front mount dovetailed into the receiver. Does that weaken the action too much where the bolt lugs lock?

Thank you for help or advice from any of you Mauser gurus.

 

[Red Leg]

First of all, anyone who would destroy an "exceptional looking" 9x57 in original livery deserves a special place in hell. Just saying.

I obviously can not see the rifle in question, but I would suggest a lot of caution on the rechamber idea. The 9.3x57 was conceived and built as a fairly light reasonably hard hitting rifle for red stag and wild boar. They tend to have what we would call on this side of the pond pencil barrels and minimal chamber walls. Grinding away metal can be a very bad idea. It is unlikely it would even be accepted for reproof in Europe.

In the 9x57 you already have a 358 Winchester equivalent. That is pretty high praise. Why ruin it?

 

[Pheroze]

The bore slugs .369” (.003” over bullet diameter) across the grooves. Will this hurt accuracy or possibly be a reason not to purchase?

I asked a similar question of the folks at Swift Bullet Co. Bill Hober called me about my enquiry (a very knowledgeable fellow and nice guy). I asked about the A-Frame which is .410 for use in the 400 H&H which is .411. He said that it would make no difference because the bullet would expand into the bore. I don't know how much can be covered by deformation. But .003 does seem like a lot. Perhaps you could speak to folks at Swift or Woodleigh about how they would expect their bullets to work in that circumstance?

 

[ACM]

First of all, anyone who would destroy an "exceptional looking" 9x57 in original livery deserves a special place in hell. Just saying.

I obviously can not see the rifle in question, but I would suggest a lot of caution on the rechamber idea. The 9.3x57 was conceived and built as a fairly light reasonably hard hitting rifle for red stag and wild boar. They tend to have what we would call on this side of the pond pencil barrels and minimal chamber walls. Grinding away metal can be a very bad idea. It is unlikely it would even be accepted for reproof in Europe.

In the 9x57 you already have a 358 Winchester equivalent. That is pretty high praise. Why ruin it?

Red Leg, this rifle is the 9.3x57 chambering. It has an octagonal barrel and plenty of meat in the chamber. All the original 9.3’s debuted very close to each other in that time period, so it would not detract from value. The 9.3 x 57 & 62 are so close to each other it takes VERY minimal reaming, and this was done frequently in days past.

 

[ZG47]

I am looking at purchasing a pre-war large ring Mauser. It is an exceptional looking rifle built by JP Sauer & Sohn.
The rifle is chambered in 9.3x57 Mauser and I have a few questions:
1) The bore slugs .369” (.003” over bullet diameter) across the grooves. Will this hurt accuracy or possibly be a reason not to purchase?
My main goal is to ream the chamber to 9.3x62. I do not want to do the work involved if the bore is out of favorable tolerance.

2) The rifle has very nice claw mounts, with the front mount dovetailed into the receiver. Does that weaken the action too much where the bolt lugs lock?

Thank you for help or advice from any of you Mauser gurus.

Rechambering one of those rifles to 9.3x62 is a bad idea because it then becomes unpleasant to shoot. I advised another hunter not to do it and later heard that he—and his shoulder—regretted the decision. The groove diameter of the barrel should be greater than the bullet diameter. Every ‘.308’ inch bullet that I have ever measured has a maximum outside diameter of .3075 inches. That includes several hundred Lapua target bullets that I need to load up at some stage. The only time you will come across a larger diameter for .30 caliber rifles is when you buy oversized target bullets which are made to extend the useable life of a target rifle barrel. NB Lead bullets should have a maximum outside diameter that is greater than the groove diameter.
All of the above is why the German army changed from the original 8x57 I rifling to ‘Z’ rifling from 1896 onward, in order to avoid core separation and occasional barrel explosions due to bullet jackets being left in the barrel. When the new ‘S’ ammunition was introduced, barrels that had been originally rifled to the ‘Z’ specification had their chambers reamed, in order to accommodate the larger diameter case neck of the updated cartridge. Those receivers were then remarked with an ‘S’.
Super tight barrels became a thing when 1,000 yard shooting required standard issue ammunition. Some of the British NRA shooters specified barrels as tight as .307 or .306 in order to gain maximum accuracy from the standard military 144-grain projectile used in the Redford Green ammunition that was issued for competition. That ammunition used .307” diameter bullets. There were, as you might imagine, significant pressure problems with those very tight barrels when the rules were changed to allow civilian projectiles which, again, have a .3075 inch diameter.
NB Notwithstanding the above comments, Steyr Mannlicher rifles with barrels optimised for homogeneous bronze/brass bullets may have very tight rifling specifications BUT those rifles are probably using—in my estimation—something like 5R rifling to minimise pressure issues.
I suggest that you leave the rifle ‘as is’ and enjoy it. 8.2x57 cases can be sized up when the Norma 9.3x57 cases are unavailable.

 

[AZDAVE]

Do you have any pictures of the rifle.

 

[ACM]

The 9.3x62 was developed in 1905 by Otto Bock to fit nicely in the standard Mauser action. I have no qualms about the rechambering.
The gun weighs 7lbs 15oz and has a nice recoil pad. I have no qualms regarding recoil either. I am not rechambering to make the gun a DG rifle, or push pressures to obtain velocity. I am avoiding having to make brass. I own a rifle that I have to fire-form, size, and trim brass for, and I am not looking to add another to the collection.
I have slugged several (~5) rifle barrels and most all have been .001” less than, .001” greater than, or equal to bullet diameter (or an obtainable bullet diameter). One was .002” greater than bullet diameter. I am not looking for exceptional accuracy, just acceptable.
Any advice regarding the bullet to bore size, or dovetail action strength would be greatly appreciated.

@AZDAVE Normally I would be more than happy to post a few pictures, but I cannot. The gun is owned by an acquaintance who has asked me not to. I’m sure he will put it up for sale publicly if I turn down the sale. Thank you

 

[Huvius]

I get what you’re saying, but my opinion is that you may just want to find another rifle.
Rechambering this rifle, which sounds like quite a fine example, is not something that would improve its value or collector interest. Quite the opposite really.

Now, to your questions about bore and the dovetail.
A .369 groove is quite large but I’d like to know if you’ve measured the bore as well. One would think that if the groove has been worn to that extent then there would be a commensurate amount of wear, or logically more, in the bore diameter.
Did you slug the bore full length from the breech to the muzzle?
That will get you the “tightest” measurement of the barrel. Now, this tells nothing of a loose bore near the breech from erosion or even a loose muzzle measurement, just the smallest measurement somewhere along the length of the bore.
You can get some idea of where that is with a tight patch on a rod to feel for the tight spot - a little subjective though.
You can also slug in from the breech a little and then push the slug back out and see how that compares to the full length slug.
Of course, one also wonders how a barrel can be over size when there are no available projectiles that size to wear it down. Very odd…

As for the dovetailed receiver ring, I wouldn’t worry about it.
Mauser did it themselves some times and they knew a lot more about the subject than any of us.
The chamber is all in the barrel and the top lug recess is always behind the dovetail so mechanically, there is nothing being changed by a properly done dovetail.
A rechamber from X57 to X62 wouldn’t appreciatively change anything in that section of the action.
The bearing of the bolt lug on the action is all on the rear wall of the recess, not on the circumferential part of the recess, in fact there is quite a bit of clearance circumferentially.
A proper dovetail is always let in well ahead of where the lug/recess interface is.
In fact, I recall a test where the receiver ring on a Mauser was taken down gradually behind the lug recess all the way to having the barrel threads exposed nearly 180deg and nothing measurable happened.
That said, there are lots of collectors who turn their noses up at a dovetailed action.
Mauser also mounted some scopes with the dovetail in the barrel just ahead of the action. These look a little dubious to me but again, this style is factory Mauser and I’ve never seen or heard of one letting go.

 

[ACM]

@Huvius Thank you for your informative response.
I slugged the barrel from muzzle to breach. I agree that the groove measurement seemed quite large. I attempted to take a reading on the bore (of slug) and did not feel it was an accurate enough measure to call definite, just due to the way the calipers have to be held to take that measurement. I know there is a better tool for the job. The rifling grooves in the slug seemed fairly deep and if I remember correctly, about ~.012 difference to the groove (bore vs groove).
As for the front dovetail, I believe it is right above the recess for the bolt lug. I found a picture on google that shows nearly the same placement as the rifle being discussed. See below.
Something I may add in regards to the value discussion. There is absolutely no place on the rifle that the chambering is stamped or engraved. There are serial numbers from Mauser & JP Sauer, Inspection stamps, & Nitro proofing marks (w/ abbreviations for steel jacketed approval). There is one mark that is a decimal, then a space, then a 66 (. 66). Maybe there was a 3 in that space at one time. In order to figure out the chambering, it had to be cast.

The above picture is not the rifle in question, it is just an imaged pulled from google showing the claw mounts installed in the same location (particularly the front dovetailed mount).

 

[pjaln]

save yourself time and aggravation , go to ralf martinis site and look at the Dittmann rifle he has for sale its under 5k scoped and its all set for you

 

[ACM]

I was able to get a little clarity on the bore from a highly regarded gunsmith today. He stated that many of the older rifle bores of that era were on the large side, and that the thicker, wider rifling would displace more metal to fill the bore. That is if the rifle has wide, thick rifling (this one does), and is not shot out.
I also ran across nearly the same rifle on GI, but it is an original 9.3x62 Mauser. Maybe that is the way to go.
Thanks all for help and advice.

 

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Another soul narrowly escaping from the darkness and flame of Mauser modding