Mauser bolt question

J

Joe Portale

New member
Hello folks,

My current project is building a BRNO 98 Mauser receiver to a 300 Win Mag rifle. I was doing some checking and found that I can buy a "Magnum" caliber bolt for this project. The modifications of the standard bolt to accept a 300 Win Mag had me a little concerned. The price for the magnum bolt is do-able. I was just wondering, is there any differences between the magnum bolt and the standard? Or are the bolts fully interchangable?

thanks
 
Joe,

I have seen bolts offered for sale that were modified to fit the base of a belted magnum, but I have never seen a "Magnum Bolt."

Which part of the modification has you concerned? I read in one of the many books on the subject that after removing material from the bolt face you would need to re-heat treat the bolt. I respectfully disagree with this for the following reason: If you are taking small cuts on your lathe and using a lubricant, then, with the possible exception of the first layer of molecules, you are not going to elevate the temperature of the bolt to anywhere near the point of reducing its BULK strength or hardness.

If the bolt face was case hardened, that surface hardening will be gone. But, surface hardening exists only to reduce wear caused by friction, and while that may be important to the bolt lugs, I fail to see the need on the bolt face which sees almost no metal to metal relative motion and when it does it is brass on steel ... I just can't see the steel wearing quickly enough for you or your offspring to notice it ... Maybe this would be a concern on an SKS shooting steel cased mil-surp, but I seriously doubt that this 300 WinMag will ever see 250 rounds through it in a day.

FWIW, mine is using the standard Turk 38 bolt.

Oh ... one other thing ... If this bolt you are looking at already has the handle turned down, that should be a source of concern ... welding CAN induce the kind of heat that can weaken a bolt, so you would want to be sure that it was done with the appropriate amount of care.

Saands
 
Hi Saands,

The part that I was concerned with is modifying the lip on the bolt face where the rim of the cartridge sildes under. There is really no need to do anything to the bolt face itself. Kuhnhausen touches on reforming of the lip to accept magnum cartridges in his book. But in typical Kuhnhausen fashion he just says remove metal to fit, but doesn't say how. My measurements tell me that the lip needs to be backed off about 0.059". This would probably be easy on a lathe, I don't have one. I can "borrow" one every once in a while, but prefer to save that favor for the threading and chambering of the barrel. I may be making much too-do about nothing. But for $90 and a clean get away, it was worth the question.

Brownell's sells Mauser actions in "mini" for .223 (my next project gun), standard for the 30.06 or 8mm case base diameter and a magnum for well, the big stuff. From what I understand, these are manufatured by BRNO and are being imported by EEA and Charles Daley. The bolt is being sold by Numerich's.

The only reason that I believe that the bolt face should be messed with is if it is pitted or showing deep wear marks. Then the face just needs to be dressed on the lath or lapped smooth. Even then, if memory serves, the safety margin is .006". Any deeper then the bolt is scrap. The bolt face doesn't carry any torque or take any real pounding, so I do not see the need for extra heat treatment either.
 
Joe,
Over the years I've come to appreciate the value of the "clean getaway" as you put it. Since you were building this rifle, I mistakenly assumed you had a lathe. I think that changes things sufficiently.

Good Luck,
Saands
 
Firstly... what is this "welding" on the bolt to which you refer? (turned handle)???

Mine are heated and bent... then filed and shaped...

as for the bolt itself... you have to fit the extractor anyway... and the amount of metal to be removed to fit the magnum head isn't much...

Me? I'd refit the original bolt to use the magnum shell head, bend and reshape the bolt handle, and fit the extractor and call it good...

I also have a few custom Mausers (pics elsewhere on this site under the "show us your hunting guns" thread)

some of which I built, some of which my Father built...

but in the end, it all gets the same job done, so it is up to you... (and there Is something to the "easy" way)
 
Hemi:

There seem to be two methods of reworking the bolts ... heating them up and bending them or cutting htem off and welding either the original back on in a different orientation or welding on a new handle. Either method exposes the bolts to heat which if not checked in some way (heat paste and a heat sink, etc) can reduce the strength of heat treated steel.

Saands
 
Hemi,

For me there is only one way to do the bolt handle, cut it off and weld on a new one. First bending the bolt shortens them. Second, heat bending them also weakens the metal.

We were not talking about the bolt handle. I was asking about the merits of re-contouring the bolt face lip to accept larger cartridges. 300 Win Mag to be specific. I found a place that sells magnum replacement bolts and was wondering if it was wiser to replace than to mess around with the original.

Saands, I have access to a lathe just about any time I want it, so why buy one? I just hate to impose on my friend who owns a jobber machine shop everytime I get an itch. Like I said in the earlier post, I prefer to save up the favors for threading and cutting the chamber on the barrel.
 
Alterations to the bolt head for larger, magnum cartridges are made with a milling machine, not a lathe. If you notice, the rim isn'r round, it's an oval shape, therefore a lathe can't make the cut.
 
The jig I use for bending bplts is about 8" square of solid steel... (heat sink from heck!)

and it doesn't shorten them ONE BIT if you hammer them in the right place... (I can even lengthen them)


but to each their own, eh?
 
Joe, if the cost of the bolt is acceptable to you then I'd think that would be the way to go. I would think that if they are billed as 98 bolts then they will work. The standard length is 6.370". Unless these come from commercial or Brevex magnums they should work fine. I would ask that before buying one but I doubt they are anything but altered standard 98 bolts. You never did mention where you were getting it. BTW, I open the bolt face with a lathe then blend the bottom with the mill if necessary. George
 
re-bolt

Dear Sir:
I do this all the time, but, I have a lathe. I first cut off the bolt handle since I'll weld on a new Brownells handle. Then I chuck the bolt body in my 3 jaw chuch (it only has .001tir.) I use a carbide milling cutter in the tailstock chuck and very carefully and slowly open up the face for the belted mag case (am building a 416 Taylor now). Then you must carefully with a dremel tool cut the lips so a cartridge will "slide up" into the bolt face. Then, weld on a new handle.
May I make another remark? Coat all three lugs with layout dye and with a complete bolt assembled see if the two front lugs are getting good contact; - NOT THE SAFETY LUG - it SHOULD NOT TOUCH.
If both front lugs don't make good full contact (actions vary) then dress the one carefully which does touch until when you repeat this both touch. Then I use fine lapping compound to dress-up the job, lapping as little as possible so as not to weaken the depth of caee hardening in the action. Re-check the safety lug IT MUST NOT TOUCH!
 
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