Not wanting to hijack FAL Grunts thread "To Coloradomatt" on machining a large ring/small thread 98 receiver to small ring profile, I'm starting a new thread. It was mentioned by one of the responders to his post, that a K. Kale large ring/small thread receiver has the thread relief cut too deep to machine safely to a small ring profile. Not aware of this, I had previously machined a 1946 K. Kale receiver to a G33/40 profile. So naturally, I am concerned about the actions safety since reading the post. I measured the receiver ring thickness at the thread relief cut on 4 receivers that I have, and here is what I found:

1946 K. Kale; Receiver ring dia. 1.298"-1.296" wall thickness min. .0895" max. .097"

1928 Radom small ring/large thread; ring dia. 1.298"-1.292" wall thickness min. .0995" max. .106"

DOT 1941 G33/40; ring dia. 1.293"-1.290" wall thickness min. .141" max. .154"

Carl Gustafs m96 1916; ring dia. 1.304"-1.299" wall thickness min. .145" max. .149"

The Radom receiver has not been scrubbed of its markings. Considering that many probably were scrubbed and that with machining tolerances on the thread relief groove, the ring wall thickness on some small ring/large thread receivers could be considerably thinner than the one I measured. My original plans were to build a .257 Roberts on the modified turk. Now ?????

Not sure what you are getting to. There is nothing wrong with your actions. I have heard people say that small ring/large thread receivers are weak, all without any proof. Measure the ring thickness on a 1917 Enfield and see what you come up with. (.104). Are those weak when barreled to 375 H&H? I have used lots of German and Polish K98s and never had a problem. And Swede 96s too.
(I do not know what a K. Kale is)

Proof?
You might measure the diameter inside (to calculate wall thickness) the ring of the SR large thread 98a. I saw one of these partly collapsed by one of those U bolt receiver wrenches. The wall thickness did not appear to be much over .050.

quote:

Originally posted by dpcd:
Not sure what you are getting to. There is nothing wrong with your actions. I have heard people say that small ring/large thread receivers are weak, all without any proof. Measure the ring thickness on a 1917 Enfield and see what you come up with. (.104). Are those weak when barreled to 375 H&H? I have used lots of German and Polish K98s and never had a problem. And Swede 96s too.
(I do not know what a K. Kale is)

Dpcd, the K. Kale is a Turkish large ring/small thread 98. I am not concerned with the strength large thread/small ring German and Polish 98 receivers. Like you I believe they have proven themselves over the last 100+ years. I guess with the measurements I took, unless the material in the Turkish 98 is suspect or inferior to the Radom receiver it is probably fine.
SR4759, I measured actual wall thickness with a Starrett multi anvil micrometer. The Polish Radom receiver is small ring/large thread.
Thanks for the replies.

Ok, you saw one crushed by an action wrench. That proves nothing. I am sure I can crush others too if I tried. What are the shooting results? I have measured them, as has Mark; not going by "appeared" to be something. Again, I am looking for instances in which those receivers proved inadequate in service.
Mark,, I have two Turk 38s waiting to be barreled now; I have used a couple in years past; no problems with them. Rougher machining is all.

Dcpd, I have used a couple of Turks without any problems also, but you are right they do take a lot more work to clean them up. Nice rifles can be made from them, although they are quite a bit looser than most actions. You mentioned the 1917 Enfield earlier,so I measured a pattern 14 Enfield receiver I have in the shop; ring overall thickness is .148" and ring thickness at the root of the thread is .102". I didn't realize they were that thin until you mentioned it.

Yes, P14s and M17s are very thin in the rings and would scare you if you thought about it very much. But they are well proven so no worry about thin rings; the stress won't be lateral, it will be aligned with the frame axis.
BTW., I crushed a Swede 96 once when the barrel would not come off and I got mad and tried to horse it off. Lesson; don't do that with a U bolt type of wrench. What does this prove? Nothing.

The crush was actually across the top of the reciever. It caved in directly in front of the locking shoulder into the space the bolt head occupies. I have seen other collapsed receivers but nothing like that.

quote:

Originally posted by dpcd:
Ok, you saw one crushed by an action wrench. That proves nothing. I am sure I can crush others too if I tried. What are the shooting results? I have measured them, as has Mark; not going by "appeared" to be something. Again, I am looking for instances in which those receivers proved inadequate in service.
Mark,, I have two Turk 38s waiting to be barreled now; I have used a couple in years past; no problems with them. Rougher machining is all.

I'll look tomorrow on the ones I have.

Dpcd,

[btw, I accidentally deleted my previous post, that asked you the question]

I was just curious to sees if any of your Turks may have the shallow thread undercut, rather than the [typical of Turk] deeper Std M98LR spec. undercut.

I know some small thread WW1 mausers had their thread undercut manufacture specs altered from DEEP[stdM98 LR spec.] to SHALLOW for the later production runs.
The knowledgable highly mauser experienced [late] Tom Burgess, suggested people avoid the small ring /Large thread[with deep undercut forward of the C-ring].

Just checked one of my 38 Turks (Ankara 1940); yes, it does have a rather generous relief in front of the threads; nothing to worry about in large ring but I would measure carefully if machining it down to a 1.3 inch ring. I also checked a Polish K98 SR Radom 1930 and it has no relief other than thread depth. I have no German K98s right now without barrels on them.

What is the minimum safe thickness?

quote:

Originally posted by dpcd:
I also checked a Polish K98 SR Radom 1930 and it has no relief other than thread depth. I have no German K98s right now without barrels on them.

When you find a Kar98a, do check it. The Poles made "adjustments" to the Kar actions.

Ok, I will but I don't find them much any more.
Minimum safe thickness? Who knows? Personally I would put it at .100 wall thickness, based on what Enfields are. And no short mags on them either. (Although, again, P14s and M17s will hold anything.)

Thanks DPCD.

(just trying to pin you down since your responses ranged from "not a problem" to "measure carefully")

I was not thinking about that deep thread relief at first.

quote:

Originally posted by dpcd:
I was not thinking about that deep thread relief at first.

Nobody does.

The dimensions I listed in my first post are the actual thickness of the receiver ring at the thread relief cut. The thread relief cuts in the Polish and Turkish receivers are cut deep enough to square up the end of the extractor cut, the G33/40 receiver is cut only deep enough for thread relief and a separate milling operation with a cutter similar to a woodruff key cutter was used to square up the end of the extractor cut.

quote:

Originally posted by dpcd:
Ok, I will but I don't find them much any more.
Minimum safe thickness? Who knows? Personally I would put it at .100 wall thickness, based on what Enfields are. And no short mags on them either.
(Although, again, P14s and M17s will hold anything.)

so the heat-treatment and metallurgy on Enfields is like that on the small ring/large thread mausers in question?

I just got an Oberndorf commercial action (circa 1912) that is large-ring small-thread. What measuring tool would I use to measure the ring thickness at the thread root. I am considering having it turned into small ring. However, I'm thinking the square bridge would just look out of place paired with the small front ring.
Matt

I like the Dressel Mauser with the Browning style Octagon receiver.

ColoradoMatt, I used a Starrett Multi Anvil Micrometer. I had to make a special anvil for it to be able to measure the thread relief without the mike body touching the threads.

I think you need to analyze the M98 receivers with the thread reliefs.

If you tighten the barrel face hard against the C ring you pre-stress that weak part of the receiver. When the rifle is fired the firing stress is added to the barrel tension stress.

If you want to minimize the stress on the reciver at the thread relief tighten only against the face of the receiver.
And don't say Paul Mauser blah blah blah until you analyze the stresses.

How much firing stress is transmitted axially to the threads? How much is generated by barrel torque against the inner collar? The answer is; "it depends" on a lot of factors. Most medium cartridges produce about 7000 pounds of axial thrust using an oiled case. (Based on a 50000 psi cartridge having a 30-06 head size) Barrel torque pre-load on the inner collar will be small in relation to the firing stress. AND, since no one shoots oiled cases, the real axial thrust on the threads will be much less; PO Ackley proved that brass can hold at least 40K psi by itself. All this is how people got by shooting rifles for the past 100 years with minimal problems. It does not take much steel to hold a few thousand pounds of pressure. I am not saying to do or not do anything; just presenting the numbers.

Plus one on Wiebes post, The guess and by gosh thats accepted as fact in the world of gundome is mighty and many..

Mr Atkinson,

were you aware that Radom mausers[early production versions with the deep thread relief] suffered from stretched collars resulting
in excessive headspace, all whilst being used by the military?

..Or do you consider it just an unfounded myth?

It was such empirical evidence based findings that caused the production arsenal to alter the manufacture of the Radom mauser from having
a DEEP thread relief,..to the then altered spec. of a shallow or non-existent relief groove.

Not Mr A, but I have never heard of that; got any data? Reference?

quote:

Originally posted by dpcd:
Not Mr A, but I have never heard of that; got any data? Reference?

I trust [the late] Tom burgess in-depth knowledge on the matter of Radom mauser collar stretch.

Just as I do the vast empirical evidence based accumulated knowledge he had and shared regarding 1909 actions
[i.e; how they suffer lug setback and the subsequent requirement for re-heatTreatment]

Of course people are fee to believe whoever they wish to believe, regarding either of the above subjects.

As I said, the Poles adjusted the SR LT actions they made after WWI. Still, even with the reduced clearance cut, manufacture was stopped in favor of the stronger std 98 action. At about the time the Poles stopped making the Kar, the Czechs rolled out the vz33 which was a SR S(mall)T(hread) receiver.

Never heard of Tom Burgess or his writings. I have indeed, had a few Arg 09 actions that had lug setback. Never had a Polish K98 with any though. No doubt the large rings are stonger; I just never had any problems with small ring 98s either. Lucky I guess.