View Full Version : Thread Pitch of Large Ring Mauser Barrel

John Lawson
07-09-2005, 12:47 PM
It says 1.10"-12 in Brownells catalog and in some of the Gunsmithing text books and manuals...HOWEVER, I read an article in HSM or MW recently where the author mentioned that the pitch is actually an obsolete metric measurement close to 12 tpi and American gunsmiths have been depitching this metric thread to 12tpi that could be cut on their lathes since just after WW-II, using receiver wrenches and barrel vises to make it fit.
It could have been an article on a subject other than guns and might have been by Marsh Collins. Can't find it. I need to find the article and obtain the precise metric pitch of this thread tenon. Can anybody help?

[This message has been edited by John Lawson (edited 07-09-2005).]

07-09-2005, 01:33 PM
<font face="Verdana, Arial" size="2">One thing that continues to amaze me Jack, is that even the most meticulous, top flight, Rifle Smiths and Barrel Makers, continue to assert that 1.10"-12 tpi, 60 deg "American" thread is "Fine" for use in the 1.10" 12 tpi 55 deg Whitworth Form thread used in the 98 Mauser receiver!</font>

I found that quote on this page:

Click Here (http://yarchive.net/metal/magnum_mauser.html)

The quote above was a little less than half way down the web page. They do discuss it a bit more after the quote above.

[This message has been edited by Carl (edited 07-09-2005).]

07-09-2005, 02:13 PM
Just my .02-

I have seen some barrels cut with 60 degree thread forced into receivers where the receiver ring was actually stretched and weakened. Dangerous as hell. Just how many fp of torque did they use?

It's not a metric thread. 1.1 X 12 tpi, 55 degree whitworth thread angle is correct. Many prethreaded barrels come with a 60 degree thread. About all you can do with a pre-threaded barrel is see if it fits in the receiver. If not, clean it up with a 55 degree threading bit until you obtain a nice snug fit. Make sure the face of the receiver ring is true. Most mauser actions are somewhat beat up on the face of the receiver and should be trued up. I have a homemade jig somewhere that screws into a 98 mauser action to allow you to spin the action between centres so you can true up the face of the receiver ring. It's pretty easy to make. If you want, I'll try and find it and post a pic for you.


Al Messer
07-09-2005, 03:36 PM
Question--why would a German industrialist adapt an English thread for the barrel shank when all the rest of the action was using the Metric system of threads?

07-09-2005, 03:49 PM
If you want that Mauser to group, it needs to seat securely against the inner ring, not the receiver face. Just make your tenon about .002" longer than the bolt face to rec'r ring measurement, then when you screw the barrel down there won't be a gap but the bbl will be seated against the inner ring.
Al, I could be wrong, but I don't think Germany adopted the metric convention until recently. 60's or 70's maybe. And we didn't adopt a standard until the mid 20's. Many of these Mausers predate all this standardization stuff.

07-09-2005, 03:49 PM
This quote is from the same web page:

<font face="Verdana, Arial" size="2">Mauser was a METICULOUS designer..He didn't choose the Whitworth form over the Metric/American 60 deg form, without a damn good reason..it being, that it is, overall, a STRONGER thread form.</font>

From what I have read, there is wide spread agreement that the Whitworth thread form IS stronger due to the generous radius at the root of the thread. That is also the problem with the thread. It is difficult to hand grind a tool. The 55 degree part is easy enough, but the exact designed in radius on the nose of the tool is somewhat difficult to do.

[This message has been edited by Carl (edited 07-09-2005).]

John Lawson
07-09-2005, 04:12 PM
Peter Paul Mauser was not the first to do this. Georg Luger used a 55 degree thread on the Luger pistol years before Mauser made Lugers. I have seen replacement Luger barrels with 60 degree threads that completely ruined the receiver ring on nice Luger pistols. The major aftermarket supliers still continue to sell the wrong threaded barrels with the thread overcut enough to "sorta/kinds" fit with sufficient pressure on the receiver wrench and a very solid barrel vise mounting.
To check this out, I bought a brand new, unfired '98 (48)Mauser made in Yugoslavia and screwed out the barrel (go ahead and scream, Mauser collectors). It is beautifully made and fitted.
Yes, it is 55 degree. Nope, it is NOT precisely 12 tpi.
Putting my Starrett thread gage on the barrel tenon, the first two thread crests fit the gage, while, for the rest of the length of the tenon, they show successively more light...not much, but perceptible.
This is what the writer I mentioned had noted. (Obviously, the longer the thread, the more deviation from ?. The barrel thread tenon is cut with a sharp pointed tool. A pre-WW-II Mauser 98 barrel from under my bench is similarly cut with sharp V form. Ergo, we are not dealing with a Whitworth form of 55 degree thread at all.
The metric system used before the turn of the last century is obsolete and no longer used anywhere. Modern metric pitch gages are useless for measuring this thread, since it was based on a different system of measurement.
The writer mentioned had the exact metric thread named and (actually) my cat jumped up on a pile of HSM's and other shop magazines and shuffled them into a pile, with no bookmark in place, so I can't find the article.
It is the precise, theoretical obsolete metric measurement that I need. (Lud Olson does not have a clue any more than Kuhnhausen has a glimmering.)
I have a new pre-threaded barrel from Brownells that does not begin to fit the recceiver threads although...the gage ring from Brownells catalog, made by Clymer, the reamer maker, slips on the Mauser's original barrel tenon loosely, full depth to the shoulder and it fits the aftermarket barrel tenon nicely also. But, the new barrel will not even start into the receiver ring.
Monday, I will order Brownells tap and die for the '98 Mauser and screw up the threads in the brand new receiver ring to fit my aftermarket barrel. I have no idea whether they (the tap and die) are 55 or 60 degree, but I have a terrible suspicion that I already know the answer to that.
The point in all this is that I'm writing a book on the Mauser and I want to set this enigma straight once and for all. Once I have the answer, I will know if most of the problems are related to lathe gearing cutting wandering threads or to misread gages.
Thank you for your help, gentlemen; it has been very interesting so far.
And, oh yes, I have two formed 55 degree cutting tool bits, one from Brownells catalog and the other from Armstrong on a round cutter bit with a feed screw. Both are dead sharp pointed...no radius is cut. Ergo, they are not precisely to Whitworth specifications, but are "kinda/sorta" to spec. (Groan.)

[This message has been edited by John Lawson (edited 07-09-2005).]

[This message has been edited by John Lawson (edited 07-09-2005).]

[This message has been edited by John Lawson (edited 07-09-2005).]

Al Messer
07-09-2005, 09:19 PM
So, it IS a TYPE of now obselete Metric thread shape instead of a Whitworth thread?

John Lawson
07-09-2005, 11:08 PM
As I said, it is a never fired rifle I bought to check this out.
The barrel tenon has a 55 degree sharp pointed thread. The Luger barrels can be cut with the same tool to make a good fit.
What I want to know is the obsolete metric pitch of this thread on the Mauser '98.

07-10-2005, 02:32 AM
From the experience that I have had with Mausers, most of them do have the 55* thread cut in them 1.1x12. I can tell you that to get the correct barrel you have to thread yourself most of the time. I have seen some that you could barely get the barrel off because of the threads being cut like you spoke of and being forced into the reciever. If you find a very good example of a Mauser, I think you will find better threads. I like the VZ24 Mauser personally because they seem to have been a little better machinist than some of the folks that manufactured them. I think most folks have found one or two that you needed to cut the ring around the barrel to allow them to unscrew. You wouldn't think a man such Mr. Mauser would use a thread that would be so hard to duplicate as to have one that varied like the one you described.

07-10-2005, 08:25 AM
gizmo2 -the barrel should seat against both surfaces. When I measure the depth to the inner ring, it is never consistent, even with the face machined square. I don't have the expertise or tooling to true up the inner ring.

When I look at all the other war time machining that occured on firearms around WW2, there's not a whole lot of consistency!

cnrtyboy1289 -I concur. the vz24's are about the most consistent, the brazilian's are good too.