Mauser barrel fitting

wedgetail · Jul 24, 2020

When cutting the barrel threads, the general consensus is to make the tenon the correct length so the inner C ring and outer leading edge contact their respective surfaces at the same time, maybe a thou or two one way depending on who you speak to. HOWEVER, the barrel I’m wanting to have profiled (original oberndorf model B)is like the military barrels in that their shoulder OD is essentially the same as the thread diameter. Meaning there is no shoulder to seat against. In general, the inner C ring isn’t 100% square (mine is 0.004” out cf the leading edge, which is 0.002” out). It seems unusual for people to lap the inner C ring, but not unheard of.

So, what is the standard for installing k98 or model B type barrels that have no shoulder? Do you lap the inner C ring to be 100% square? Do you not worry about 0.002”? Do I try and obtain (or make) a C ring lapping tool? Other option is I could get the shoulder cut say 0.050” - 0.100” wider to give it something to seat against - wouldn’t probably be overly noticeable. Then I could cut the tenon say 0.002” short and have most of the bearing surface on the (easily squared) leading edge)? I won’t be scoping this rifle, will the difference be noticeable? I doubt the inner rings wear, so I assume they wouldn’t have minded the 0.002” discrepancy at the oberndorf factory.

4575wcf · Jul 24, 2020

The immediate predecessor to the M98 German Service Rifle, the M88 Commission Rifle, had no provision for a barrel shoulder whatsoever, as did our own Krag Jorgensen. I own both, and they work and shoot very well. I have read that the idea was to "load" the threads against the force of firing by bottoming on the collar and drawing them up. Most references advise to set the collar to contact first by a slight amount when using a shoulder. Personally, I would cut them that way, and I would go to the extra trouble to cut the 55 degree Whitworth thread form. As for the .004 out of square, it depends on the application. On a hunting gun, I would let it slide. If I was taking it to the high power finals, I would square it up dead nuts.

Konrad308 · Jul 25, 2020

I am following this as i am not sure what the correct way is and there is a lot of conflicting information on this toptic if you research it.

I dont have a lot of experience with Mauser or Mauser type actions. I have turned off only 3 and 2 of the 3 had full contact with the inner c ring and no contact with the shoulder and the other no contact on the c ring and full contact with the shoulder.

I think the shoulder contact is not necessary but would not hurt to have the extra support of both the inner c ring and the shoulder contact.

I dial the action to square the inner c ring with the raceway. (this i am also not sure if it is necessary given the amount of play on the bolt) at the same time i true up the shoulder.

I agree with the 55° threads.

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akajun · Jul 25, 2020

On a large ring style Mauser with an inner shoulder your better off fitting it to the inner shoulder and giving .001-2 clearance on the outer shoulder, especially if your not truing the face of the reciever. Trying to fit it on both shoulders does something funny on the accuracy, they’ll shoot kinda ok but not as good as when it’s clearanced

michiganbuck · Jul 25, 2020

IM not a gun smith and my gun work was limited to OD finishing barrels, making gun reamers and cosmedic sporterizing 98s....but I found this on 98 threads and thought it interesting. I have a gunsmith insalled high class barrel on my 98-06. Never benched it or did any match shooting, just a nice hunting gun.
Mauser 98 Barrel Threads - Barrels - Military Firearm Restoration Corner

mac1911 · Jan 11, 2021

how did this project work out for you,

I have a dou 1944 action and a NOS Israeli 308 barrel. They do not thread together nice.Around a rotation and a little and it locks up.
It appears the Israeli 308 barrel maybe the 60' Threads vs the 55' on the Receiver. Brownells has a 60' tap and die will this be sufficient if I chase the existing threads with the 1.10" x 12 tpi 60' tap and die ?

john.k · Jan 11, 2021

I would advise against getting a tap and die......the expense is unwarranted ,and there is a good chance the die will overcut the soft barrel steel,and you will have a loose fit.......In such a situation ,I would try lapping the threads with some fine abrasive(one of the bore lapping pastes would do)......you will be surprised how quickly the two will fit together.

mac1911 · Jan 11, 2021

I was considering renting the tap and die from $d rental.
What grit lapping compound? I have some "valve" lapping compound handy I dont think it mentions the grit

mechanist · Jan 11, 2021

I would also recommend trying to lap the threads first to see if that works. The problem with the receiver tap is that the receiver is case hardened, and the metal might be really hard. Unless the threads were obviously damaged I would hold off on running a tap through them. Also, did the barrel that came off unscrew OK? If it did, then the problem might be the surplus Israeli barrel, not the receiver. Just something to think about: The receiver legally is the firearm. Everything else are just parts. Parts can be easily replaced - the receiver can't. I'd try doing the working and fitting on the "parts" first, and only modify the receiver as a last resort.

kendog · Jan 12, 2021

mac1911 said:
how did this project work out for you,

I have a dou 1944 action and a NOS Israeli 308 barrel. They do not thread together nice.Around a rotation and a little and it locks up.
It appears the Israeli 308 barrel maybe the 60' Threads vs the 55' on the Receiver. Brownells has a 60' tap and die will this be sufficient if I chase the existing threads with the 1.10" x 12 tpi 60' tap and die ?

Lap it with fine Clover valve paste and you will be good. I do this quite often when customers want a surplus or used barrel put on their 98's.

gbflyer · Jan 12, 2021

I asked this same question on Africa Hunting forum assuming that there would be more feedback from an international community of shooters. So far the only 2 replies I have gotten are to contact both surfaces. I’m putting parts together for a build on a left hand Zastava. Unless I get definitive advice I’m gonna contact both. If it doesn’t meet my expectation of being accurate enough for a classic hunting rifle, I’ll relieve the front and try it again.

mac1911 · Dec 3, 2022

I finally finished my 308 conversion on my rifle. Took a little cleaning and some fine compound. Once I got about 4 rotations deep it cleared up and threaded on nice. Came out great. Shoots so much better. The hardest part was getting the soldered on cleanly.

wesg · Dec 3, 2022

Re lapping a thread, unless you can go all the way thru and come back, you're going to lap a taper. Not necessarily bad ... have to think about seating on the inner shoulder ... I think taper lends itself to better thread engagement if it seats on the outer shoulder.

*****

If it shoots, it shoots.

I rebarrelled a Norwegian Krag for a friend. Set it up to seat on both faces, after I trued the front face. Main reason was to open it up so I could avoid turning the breech of the barrel down to fit inside, and having to polish it. Three times the work, but ...

Torquing it up, it barely moved at all. Saw some groups it shot, after turning the barrel down twice to take weight off it. Rather surprising for a rifle put together from a shoe box of parts he found in his attic, and a 'cheap' (Shaw) barrel.

***** I think Viper (Stiller) started out making his actions this way, tapered thread, based on engineering data from Aerospace work. And after a number of 'gunsmiths' ignored the instructions to cut the thead to a specific pitch diameter and siezed them in the actions, he gave up ...

clarkmag · Dec 5, 2022

I print this blank drawing... fill in the dimensions... tape over the lathe splash guard.

I like the C ring to touch =.002" before the shoulder.

john.k · Dec 6, 2022

In fact a standard 98 action will have only 5 full threads,consequently the experts say to never use a relief in the tenon thread,or there will be insufficient thread engagement.

mac1911 · Dec 8, 2022

wesg said:
Re lapping a thread, unless you can go all the way thru and come back, you're going to lap a taper. Not necessarily bad ... have to think about seating on the inner shoulder ... I think taper lends itself to better thread engagement if it seats on the outer shoulder.

*****

If it shoots, it shoots.

I rebarrelled a Norwegian Krag for a friend. Set it up to seat on both faces, after I trued the front face. Main reason was to open it up so I could avoid turning the breech of the barrel down to fit inside, and having to polish it. Three times the work, but ...

Torquing it up, it barely moved at all. Saw some groups it shot, after turning the barrel down twice to take weight off it. Rather surprising for a rifle put together from a shoe box of parts he found in his attic, and a 'cheap' (Shaw) barrel.

***** I think Viper (Stiller) started out making his actions this way, tapered thread, based on engineering data from Aerospace work. And after a number of 'gunsmiths' ignored the instructions to cut the thead to a specific pitch diameter and siezed them in the actions, he gave up ...

All I can say is there was some sort if rust burr or galling about half way on. A little lapping and just a few turns it broke up what ever it was. Then the barrel spun on nice and locked up tight on the receiver and as best as I could measure the inner shoulder and barrel shank depth it should have just bottomed out.
I borrowed a book from a friend Mauser Shop manual K98 by Kanulous < spelling is incorrect. 75ftlbs so far no problems. Even the sights I soldered on are still in place!
That was a worry for me.

clarkmag · Dec 11, 2022

I have shot with 5 foot pounds of torque and 1000 foot pounds of torque on clean lubricated Mauser threads. They both shoot the same.

wesg · Dec 12, 2022

'Kuhnhausen', I think.

I've run into the same thing, not necessarily an action. Some sort of crud in there, a little 'Clover' compound and it's good to go.

I've even been known to use one of my insert threading bars as a scraper ... don't tell anybody ...

Mauser barrel fitting

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