Can Somebody Tell Me?

[HollowPoint]

I've searched everywhere I can think of on the internet but for some reason I can't seem to come up with the specific answers I'm looking for. It has to do with the K31 Swiss rifle.

I'm trying to find out what the thread pitch is on the barrel tenon. I don't know if it's a metric or SAE thread pitch. I've asked on other forums where one would think the answers could be found but all I got were long winded lectures by well meaning people and return inquiries asking me why I want to know.

My reason for not stating why is because I know from experience the onslaught that will follow from the milsurp purists. In an effort to avoid awkward situations, I'd rather not say right now.

I used to have this specific info in my possession a few years back but the paper I had written it on has vanished off the face of the earth. I got it from the only gunsmith I know of that works on K31 rifles. (Larry@LRPgunsmith) He was nice enough to send me this info via email, but like I eluded to; I lost it.

I've reached out to this same gunsmith for the same info but have yet to hear from him. I figure he gets a myriad of stupid question all the time so he may never reply to my request for this same info. If you can help me out that would be excellent. If not, that's OK too; just, no lectures please; and thanks in advance.

HollowPoint

[akajun]

THe greater issue is that the end of the barrel has a cam milled into it that is very difficult to produce without CNC, or at leased a geared rotab/dividing head, that rotates the straight pull bolt. THis is why most people who re barrel these simply leave the old barrel in place, cut it off, and "barrel Stub" the old barrel, threading the new one into the old stub so as not to have to recreate the cam. This may also be why you cant find the thread pitch.
As far as purists, its your gun, theres tons of them out there, have at it, just keep that in mind.

[Artful]

Yep not an easy swap
http://www.lprgunsmith.com/K31_rifles.htm





Barrel Work









Because of the complex angles and cuts at the breech end of the K31 barrel, a bushing must be made from the old barrel in order to fit the new barrel. This adds an additional cost to the initial rebarreling of the rifle. This is a one-time cost and does not have to be repeated for any subsequent rebarreling.















Prices






Convert original barrel to accept replacement barrel
$135.00




Install Customer's Barrel
$300.00




All barrels must have minimum breech diameter of 1.100” and have a straight
section 2.500 long or longer at the breech end to be used as a replacement barrel.








In House Barrels:


Krieger Stainless (28" or less)
$630.00





Douglas Chrome Moly (26" of less)
$455.00





Barrels by other manufacturers (Does not include cost of barrel)

$323.00

[HollowPoint]

I've read and re-read all the info I can on K31 gunsmithing. The references posted by you guys who were kind enough to reply is part of the overall information I've collected over time. From the day I brought my K31 home, I've made it a point to tweak it to my preferences. For the most part, I've done just that. Right now the only piece of the puzzle I'm missing is the thread-pitch info.

I did receive a reply from Larry over at lprgunsmith.com but all he did was state the obvious. The fact that he replied at all is a positive sign of his character but, he included no specific info. I guess I'll find out that specific info myself when I take my barrel off. I was just hoping to get those thread dimensions ahead of time so I could do some practice runs on the threading whenever I got some free time.

I'm neither a gunsmith nor a machinist so I don't like to just dive right into projects like this without first taking baby-steps. It generally takes me a couple of tries to get it right. If I had those thread pitch specifics I could have gone ahead and cut some practice tenons before cutting the real thing.

I've been told repeatedly, almost verbatim to one of the previous replies that the K31 had complex angles and difficult geometry and this-that-and-the-other. When I look at pictures of the K31 tenon and how it indexes in the receiver, I really don't see it as being all that complex; although, I do see the absolute-need for being meticulous about such a job but, you have to do that anyway when you re-barrel or re-chamber.

In situations like this where specific information is sparse; (not because no one has it but because it appears to be more of a trade secret than anything else) I tend to believe that those who do have this information may fear that it will cut into their profits if they were to give out that information. Yea, I know; conspiracy theory gone amuck but, it just seems that way.

Thanks for posting guys.

HollowPoint

[Cap'n Morgan]

I'm trying to find out what the thread pitch is on the barrel tenon. I don't know if it's a metric or SAE thread pitch. I've asked on other forums where one would think the answers could be found but all I got were long winded lectures by well meaning people and return inquiries asking me why I want to know.

According to this site the pitch is 16 tpi.

http://www.kammeret.no/forum/viewtopic.php?f=38&t=1478

I searched for pictures of Nagant barrel threads and don't see what all the fuss is about. A lathe with a milling attachment and some fingerspitzgefuel would probably do the trick.

[HollowPoint]

Greetings Cap'n Morgan:

I checked out your link but couldn't seem to find my specific rifle listed on that page. I may have looked right at it and missed it since alot of the writing is in a language other than english or, maybe something else is amiss.

I'm looking for the barrel thread pitch for a K31 Schmidt-Ruben 7.5x55 rifle. I noticed you mention a search for "Nagant" barrel thread pics. Could it be that we got our rifles mixed up? If not, can you be a little more specific as to the location on the page link where you found the "16 tpi" you refer to?



Thanks

HollowPoint

[Cap'n Morgan]

Hollowpoint, my bad! I somehow got the idea you was talking about a Nagant. Still, it should not be that hard to machine. As for the pitch; can't you measure what you have with a thread gauge? On such an old rifle I'm almost 100% sure the thread is imperial 55 degree and probably also an even number, 12-14 or 16 tpi.

[HollowPoint]

Hi Cap'n:

I vaguely recall Larry over at lprgunsmith emailing me with a 16 tpi number but it was so long ago that I can't really remember. I'm hoping it is a non-metric thread pitch. Not because I can't do metric threading on my lathe; it's just that I've only ever done imperial threads and doing metrics entails the use of different gears.

When I re-barreld my Enfield, it turned out to be a 14 tpi but they have since gone to the metric system with most stuff they build now days.

It stands to reason that since these rifles were built during the WWII era and alot of countries weren't yet using the metric system, they most likely are imperial threads but I won't know until I remove the barrel. I'm just waiting for certain items to come back in stock at my seller of choice before I proceed any further.

In the mean time I'll be making up a barrel-wrench to remove the receiver while I'm waiting.

HollowPoint