Torquing a mauser barrel, Inner C ring or face?

[Shawnba67]

Has there been any consensus on best place to torque against for accuracy?
Ive heard both ways but Im betting someone on here has built a handful of target 98's and has a justifiable preference?
Or maybe it is no matter at all ?

Action has been faced off on mandrel between centers.
Thank you very much for any sage advise.

 

[Preacher]

They need to hit both places at the same time......

 

[kendog]

When I cut a barrel for a 98 I go for both surfaces. The inner ring is seldom absolutely square with the rest of the receiver. With a match quality barrel and good barreling practices they tend to shoot real good. Did one a while back for a customer in 7.62 X 39 Lapua and a .308" 14 twist Krieger and it consistently shoots .5 moa.

 

[gat]

Many of the commercial Mausers FN etc made contact inside and the barrel shank was clear of the action by 2 or 3 thou.
I have barreled more than a few{4 or 5 hundred or so} and I always trued the front ring and letting the barrel make good contact there. I think they shoot better with just one point of contact. Just my 2 cents!

 

[tobnpr]

The military contour barrels had a relatively small diameter as compared to the receiver, so not much bearing surface.

Prefits, such as those by Shilen, are short chambered, designed to bear only on the outer ring which makes them "user installable" without a lathe- that's the market for them. I'll typically install them to contact both, but only because it's relatively simple to do and not because I believe it makes a significant difference in accuracy.

Flies in the face of logic IMO to suggest otherwise. If having an "inner ring" to seat the breech were beneficial to accuracy you'd see it on precision custom bolt actions.

JMO, YMMV.

 

[Someoldguy]

I have a K98 with a Zastava take-off barrel in .308Win 12 twist that threaded up perfectly on the shoulder and head spaced perfectly with -0- adjustments required.

It is the most accurate factory barrel I have ever owned.

Bolt rattles around like a 1/2" bolt in a 3/4" hole, too.

I can't say if this is 'right', 'wrong' or 'indifferent'. All I know is it shoots fantastic.

Sometimes, it doesn't pay to think too much is all I know.

 

[Someoldguy]

They need to hit both places at the same time......

I'm not going to attempt to disagree, but I am curious.

How do you get both surfaces to contact exactly the same amount?

Out to how many places, and how do you measure this?

 

[Will Henry]

I cut the tenon .002" short so it seats hard on the receiver ring and hits the inner barrel seat when it is torqued on. Once the barrel hits that seat, it stops pretty solidly. WH

 

[hpshooter]

From The Mauser Bolt Actions M91 through M98 A Shop Manual by Jerry Kuhnhausen, pg 182.

" When barrel thread extension length is correct, the rear barrel face and the barrel torque shoulder will contact the receiver's primary and secondary shoulders at exactly the same time" Kuhnhausen then states that the secondary shoulder should be clearanced .001 t0 .0015" and they will draw up tight when torqued to 65-70 ft. lb.

Tenon length is measured with a depth mike in 3 places on an un-trued receiver, one place on a trued receiver.

Supports what Preacher has stated. I have no opinion since I have never done it, do have a single shot FN action to do at some point in time.

 

[Riesel]

Since we're just throwing techniques around, I'll thread the barrel four-six thousand longer on the tenon that the depth from action face to inner ring. I'll hand tighten action on to the barrel and keep trimming barrel breech face until I have a .002 gap between action face and barrel shoulder. Chamber barrel, screw and tighten together with 60-70 pounds (just about all I can pull with a 20" cheater bar). Barrel shoulder is snug on the action face and I feel this gives me major contact on the inner ring. Doing load development on a recent 6.5-.284 build and it's showing promise.

 

[Shawnba67]

If you are bottomed out on the inner ring and pulling down on the outer. This about has to put some odd stress on the tennon doesnt it? I mean the one on the inner ring is pushing up/out on the tennon the one on the face is trying to compress that 1" of tennon while the first one is stretching it. (Miniscule amounts I know)This only applys to the crush fitting of both, the barely touching for astetics reasoning seems logical.
Now I have no idea if this is desirable,
But not many other actions ever copied this particular design feature of the mauser rifle .

 

[Stan Taylor]

Here is a picture of a barrel I removed from a FN action made in Belgium that I have to duplicate the original profile so it goes back in the original stock it shows some evidence of touching inter ring an outer ring which that tells me whoever installed this they made every attempt to contact both places what is right or wrong can't give a pro or con of either way look real close an see if you pick up anything else unusual.

 

[Preacher]

Here is a picture of a barrel I removed from a FN action made in Belgium that I have to duplicate the original profile so it goes back in the original stock it shows some evidence of touching inter ring an outer ring which that tells me whoever installed this they made every attempt to contact both places what is right or wrong can't give a pro or con of either way look real close an see if you pick up anything else View attachment 1037765 unusual.

Flat crests seem a bit odd compared to the usual.....

 

[Riesel]

Shawn, I don't know enough about it to make a stress call. My reasoning is that since I did a snug up hand tightening setting the tenon length the breech face will make a light contact with the inner ring and when fully tightened the .002 disappears with the crush fit. I was told by a well qualified smith that you want most of the torque on the inner ring and lighter contact on the action face/shoulder. Maybe a ninety/ten or an eighty/twenty. I don't know what the .002 gap equates to when fully tightened. Stan, when I have removed barrels off old 98 actions I see were the inner ring is always in contact with the breech face and the shoulder to various degrees depending on the rust. When I look at your picture what I really see is "Whoa, get a load of them threads "
Robert

 

[Stan Taylor]

Shawn, I don't know enough about it to make a stress call. My reasoning is that since I did a snug up hand tightening setting the tenon length the breech face will make a light contact with the inner ring and when fully tightened the .002 disappears with the crush fit. I was told by a well qualified smith that you want most of the torque on the inner ring and lighter contact on the action face/shoulder. Maybe a ninety/ten or an eighty/twenty. I don't know what the .002 gap equates to when fully tightened. Stan, when I have removed barrels off old 98 actions I see were the inner ring is always in contact with the breech face and the shoulder to various degrees depending on the rust. When I look at your picture what I really see is "Whoa, get a load of them threads "
Robert

I new some one would notice I have to grind a thread tool an determined the thread pitch that's the second one I have seen in my life.

 

[Ggmac]

I'm not going to attempt to disagree, but I am curious.

How do you get both surfaces to contact exactly the same amount?

Out to how many places, and how do you measure this?

Plastigauge is the easiest . But for accuracy , I build all mine torquing to the inner and have .001-.003 clearance on the outer . I only use the outer IF the inner is not square .

 

[Shawnba67]

I new some one would notice I have to grind a thread tool an determined the thread pitch that's the second one I have seen in my life.

Do the reciever threads match? (Is that what they were trying to do)
Reminds me of the square threads on my benneli shotgun choke tube!

 

[Stan Taylor]

Do the reciever threads match? (Is that what they were trying to do)
Reminds me of the square threads on my benneli shotgun choke tube!

Yep

 

[Cloudrepair]

View attachment 1037781 Here is a picture of a barrel I removed from a FN action made in Belgium that I have to duplicate the original profile so it goes back in the original stock it shows some evidence of touching inter ring an outer ring which that tells me whoever installed this they made every attempt to contact both places what is right or wrong can't give a pro or con of either way look real close an see if you pick up anything else View attachment 1037765 unusual.

Is that a acme thread?

 

[butchlambert]

Yep

Well, Looks like the fellers have never seen square threads. I have a few rifles with square threads. I'm kinda like Cgmac on fitting the tenon. I do use the proper 55 deg thread instead of 60 deg.