Re-Barreling/Re-Chambering my K31 Swiss

[HollowPoint]

It's been a long time coming. I've dreamed of doing this since bringing this rifle home.

Why? There are many reason I can come up with but, to anyone asking "Why," no reason is good enough. Lets just say I'm tweaking an already very-good rifle to my own preferences.

On Wednesday I had the day off so I made an action-wrench shaped specifically for the K31 receiver. On ThanksGiving morning I used this action-wrench to remove the barrel from the receiver and I was surprised to see how close the tolerances were of this old Swiss rifle. For being a rifle built pre-CNC, it is really surprising to see this level of accuracy.

From the measurements I was able to get off of the receiver, it looks like "Truing-The-Receiver" won't be necessary. I'll have to wait till I get farther along to do double check though.

The barrel threads appear to be metric. I say this because my standard thread pitch gauge had nothing on it that would fit the threads on the barrel tenon. I'm presently waiting on my newly ordered metric thread pitch gauge to arrive. I'll be taking lots of pics as I move along with this project; and I'll be doing this job my own way.

I have to state up front that I'm not a gunsmith and I'm not a machinist. I'm sure there are several ways to go about this but as I've just stated, I'm doing it my way; which may or may not be the right way.

I generally don't post my projects any more until after I've completed them. This is due to the ever present Trolls, Nay-Sayers and well-meaning Dream Killers; as well as the Self-Appointed-Experts. Few things are worse than one of the above trying to tell you how to do something when we know that it's not likely they've ever undertaken such a project themselves. Insight from those with hands-on experience is always welcome and appreciated; negatives from the Self-Righteous and All-Knowing among us, not so much.

Following is the list I made pertaining to this project. I laid it out for myself. It's in the general order that I'll be approaching this project. And, I forgot to mention; I'll be re-chambering to 6.5 x 55 Swedish.

I'll be back with updates as they happen.

HollowPoint

K31 Re-Barrel Project


Materials needed:
(1) Steel for Making Action/Receiver Wrench--Two Large Bolt/Washer/Nuts Done
(2) Steel Tube for Bolt/Receiver Truing Fixture--Eight Bolts/Spiders Done
(3) Wood for Barrel Vice Done
(4) Drill Rod for Truing Receiver Done
(5) 4140 Rod for Making Barrel Nut and Recoil Lug--2" diameter 4" long Done
(6) Dykem Layout Dye Done
(7) Barrel--Chamber Reamer--Range Rod--Go Gauge--Loading Dies--Brass--Bullets Done or On The Way


Measurements needed With Barrel Still On The Receiver:


(1) Back Of Receiver to the Breech Face =_______ Done
(2) Back Of Receiver to the Cam Face =_______ Done
(3) Back Of Receiver to the Case-Head =_______ Done


Measurements Needed With Barrel Removed From Receiver:


(A) Front of Receiver to the Receiver Lugs =_______Done
(B) Front of Receiver to the Bolt Face =_______Done
(C) Front of Receiver to the Bolt Lugs =_______Done


Steps In Sequence:


(1) Check Bolt-Lug Contact Before removing Barrel (Lap Lugs if Needed) Done
(2) Remove Barrel from Receiver Done
(3) True Up Receiver, Receiver-Threads and Bolt-Face Done
(4) Measure New Receiver-Threads for New Tenon Dimensions Done
(5) Index Barrel in Lathe and Cut Outside Tenon Dimensions Had To Go To Plan-B
(6) Cut Threads Done
(7) Short Chamber With New Chamber Reamer Done
(8) Dykem Barrel Tenon, Screw into Receiver, Mark Extraction Notches and Cam Position Had To Go To Plan-B Done
(9) Make Cam Template with aluminum sheet metal Done
(10) Remove Barrel from Receiver and Cut Extraction Notches and Barrel-Cam
(11) Make Barrel Nut and Recoil Lug Had To Go To Plan-B
(12) Assemble and Head-Space
(13) Make New Scope Mount Done
(14) Disassemble and Powder Coat Flat Black then Reassemble. Done (I Powder-Coated while I was waiting for the new barrel to arrive; also sanded and refinished the stock.)
(15) Safety/Function Testing Done--Project has now been completed and Proof-Tested successfully.

[Wolfer]

Well I don't consider myself as a Troll, nay-sayer or dream killer and I'm not an expert at anything. I am though a pretty handy feller who often thinks outside the box. I believe I recognize a kindred spirit.

While talking to a co-worker about my latest 34-57 project he asked why, I replied that because I could.

I look forward to seeing this project unfold.

[skeettx]

6.5x55 COOL!!
Whose barrel?
Thanks for posting
Mike

[gzig5]

Curious as to how you plan on cutting the extraction cam surfaces in the rear face of the new barrel? Definitely post pics.
Every re-barreling of the K31 that I am aware of being done outside of at the factory in Switzerland, has utilized the old barrel stub bored out to fit a new barrel in order to retain these surfaces because of the difficulty in reproducing them.

[Outpost75]

Do you have plans for the pull-off K31 Swiss barrel? If you keep the breech for a stub, that is OK, my plans for it would be to have John Taylor fit the remainder to an H&R .44/.410 shotgun receiver and chamber it in .30-30 for a light walking rifle.

[HollowPoint]

Thank you so much Wolfer:

I'm afraid I come off as abrasive and end up turning people off when I pre-empt my posts in such a way as I have but I've had more than my share of negative comments, opinions and suggestions on alot of my previous projects (not so much on this forum but on the internet in general) that I tend to put up a shield without thinking what an offensive turn off it can be.

My apologies to everyone for this character-flaw on my part but, I can't help but think of all those potentially great ideas that have been stifled before they're even attempted simply because of a well-meant but misspoken word.

I know I'm not the only dreamer here. I also know from my research into the subject of re-barreling the K31 rifle that I'm not the only one who has considered doing the same with their K31's as well. I hope to be informative enough to dispel the deeply entrenched myth that the K31 rifle is to hard for the home gunsmith to re-barrel/re-chamber; it's to complex, it's to expensive, it's not worth the trouble, etc, etc, etc.

Having taken mine completely apart, it doesn't look all that complex to me. Perhaps that's one of the benefits of being ignorant. If I knew better I might not ever accomplish anything. It does have some angles that other rifles do not have but, most of those angles will not require altering of any kind.

For example: By blacking them out with a sharpy, I checked the angled contact surfaces of the Bolt-Lugs as they rubbed against the Receiver-Lugs just to see how evenly they were making contact. Looking at them with the naked eye, they appear to be perfectly even. The wear marks on the Receiver-Lugs show the same even wear. Oddly enough, the faces of the Receiver-Lugs are machined at an angle matching the angle of the Bolt-Lugs so it's a good thing they're wearing evenly. It means that I don't have to alter them to get them to contact evenly.

If I had to even them out myself, I'm really not sure how I'd go about it. I'm sure I'd think of something but, thank God I don't have to.

One of the things I'm having to do now with this project is build specialty jigs in order to do some of the operations that will be needed here. I've already made my Action-Wrench and it worked like gang-busters. Next I'll be putting together my Receiver-Truing-Jig followed by the Specialty-Truing-Rod I'll be using to check to see if the face of the Receiver will need to be trued. From some of my preliminary measurements, I found that the receiver face may not need truing.

Well, I'm starting to ramble on without saying a whole lot that you probably don't already know. Thanks for the encouragement. I'll be back as I get farther along. I've already taken a few pictures. I just have to edit them for posting on the web.

HollowPoint

[HollowPoint]

Do you have plans for the pull-off K31 Swiss barrel? If you keep the breech for a stub, that is OK, my plans for it would be to have John Taylor fit the remainder to an H&R .44/.410 shotgun receiver and chamber it in .30-30 for a light walking rifle.

My original plans for the take-off barrel is to keep it until I reach the end of this project. I'm fairly confident I can pull this off if I take my time and remain meticulous about each step in the process. When I've completed everything and confirmed that it was a success, I'll then consider selling the barrel to recoup some of the expense of this project.

Right now the barrel has the Rear-Sight fixture removed so it's just a naked barrel. It actually came loose while I was removing the barrel from the receiver. I think it's just soldered into place at the factory. It's been my plan all along to re-barrel without having to cannibalize my existing barrel. As a fail-safe, and if worse comes to worse, I can reinstall it back onto my receiver until I can raise the spare change to try it again.

skeettx/Mike asked, "Who's Barrel?" If you mean what barrel brand I'll be using, I plan on using a #4 contour Shilen barrel. I'll have to order one with some added diameter on the chamber end of the barrel blank just so there's enough meat to cut my threads. If I read it correctly, Shilen's website states that I can order a barrel with "Added Diameter" on any part of the barrel blank. I'll be contacting them next week to confirm this.

I'll have to wait and see.

HollowPoint

[M-Tecs]

I haven't re-barreled any of mine. Most choose not to cut extraction cam surfaces and go the barrel stub route.

LPR has an excellent reputation. www.lprgunsmith.com/K31_rifles.htm

[HollowPoint]

I haven't re-barreled any of mine. Most choose not to cut extraction cam surfaces and go the barrel stub route.

LPR has an excellent reputation. www.lprgunsmith.com/K31_rifles.htm

Yes, I've heard good things about this gunsmith. In fact, I've contacted him myself on a couple of occasions while doing research into this re-barreling job. On both occasions he was kind enough to reply. To me, that's a sign of integrity.

Virtually every time I went online to try to dig up more new information on this project, Larry at lrpgunsmith.com came up. That not only speaks of his expertise on this subject but also to the near total lack of general gunsmithing information about this particular rifle.

At first I thought it was because those who did know just didn't want to share, but now I see that all of those things you read on the internet about this rifle being so hard to work on is just deeply entrenched hear-say; so much so that it appears that very few even bother trying.

Who knows, I may find out the hard way that they were all correct in their assessment of the difficulties of working on K31 rifle barrels. On the other hand.........


HollowPoint

[ratboy]

Well I don't consider myself as a Troll, nay-sayer or dream killer and I'm not an expert at anything. I am though a pretty handy feller who often thinks outside the box. I believe I recognize a kindred spirit.

While talking to a co-worker about my latest 34-57 project he asked why, I replied that because I could.

I look forward to seeing this project unfold.

i built a 357 maximum marlin lever just because i thought i needed to.
i think a 6.5 k31 sounds like enough fun i might have to buy another rifle to take apart.
i think it is probably a good thing we all live so far apart. i dont want to know what kind of mayhem we would get into as a group.

[HollowPoint]

Here are a few pics of my K31 after disassembly.

Right now I'm working on my Receiver-Truing-Jig. Once I get that done I can check the receiver to see if it will need to be trued to the axis of the bore. I'm hoping it won't but if it does need it, I'll be prepared for it.

After that I can order my new barrel and while I'm waiting for it to show up I'll move on to laying out the shapes of my Barrel-Nut and Spacer.

The "Spacer" will sit between the Barrel-Nut and the front receiver face. It will be the attachment point for my scope mount.

Previously, the front of my scope mount was attached within the factory rear sight trough using the same cross-pin and an additional screw. WIth the factory rear sight trough gone, I needed to come up with another way to secure my scope mount to the front of the receiver. I don't want to drill any more holes in my receiver so, the "Spacer" is what I came up with. I'll have to fabricate it before I can show it to you but, now I'm getting ahead of myself.

Enjoy the pics. Hopefully they'll give you a good idea of what I'm working with. I'll be back.


HollowPoint

[ratboy]

neat.

[Plate plinker]

No guts no glory my dad always says. Good luck.

[HollowPoint]

Thanks Plinker:

I appreciate that. I'm not really looking for "Glory." I'm just wanting to dispel some of those K31 Old-Wives-Tales. Although, some of those Old-Wives-Tales are so deeply entrenched that I'm sure they'll live on no matter how much proof is offered up to dispel them.

It's kind of like the "Climate-Change" thing; for lack of a better analogy.

To anyone who's reading this right now. Do an internet search on the subject of Re-barreling a K31. What you'll get is a whole lot of the same thing. In many cases, word for word repetition to those that have inquired about how it's done or the feasibility of doing it themselves.

Also; the older I get, the less I like the feel of recoil on shoulder. I think that going from 7.5x55 to 6.5x55 will help a little in that regard. And yes; I know that I could simply power down my existing loads and save myself alot of work and potential failure but, that just skirts around the point of this whole project. I want to do it myself to prove to myself that I can do it; and to prove to others that it can be done by them as well.

HollowPoint

[EDG]

[Wolfer]

When I was young say 20 or so I traded guns some. Often buying something that needed work. Fixing it up and reselling it. I wanted to build a rifle on a Mauser action. I bought a pistol in a cigar box with no two pieces together for $20.00 Supposedly it was all there, it wasn't. I had to make the hand and spring and time everything. Also had to make grips for it.

Traded it and $12.00 for a 98 Mauser in 7.65 argentine. Now I was ready to build my rifle but I didn't know where to start. Everyone I talked to said the same thing. Forget about it and leave that stuff to people who know what their doing. My question was how do people who know what their doing learn what their doing. There was no Internet back then and finding a place to start was slow. Eventually I got some books on the subject and met a gunsmith who was willing maybe even eager to help me along.

Once I built my first rifle myself I realized I could have done this years ago but I listened (somewhat) to all the nay Sayers and dream killers out their.
I made some mistakes on my first one and on my second but any school you go to charges a tuition. The school of hard knocks is no different.

I have found there's a direct relationship between how much your tuition costs and how much you learn!
Woody Roberts

[skeettx]

General question, does the action have the capacity of conversion to 243 Win or 6mm Rem?
Is the 57mm of the 6mm Rem ok with the shorter bullets overall length?

[HollowPoint]

General question, does the action have the capacity of conversion to 243 Win or 6mm Rem?
Is the 57mm of the 6mm Rem ok with the shorter bullets overall length?

This most likely won't answer your question directly but it may give you a general idea of the answer you're looking for.

I chose to re-chamber to 6.5x55 because it's a cartridge similar in dimension and lower in Maximum-Average-Pressures than the original 7.5x55 Swiss cartridge. I wanted to make sure that the K31 action could handle the pressures of this or any cartridge I originally had in mind. As it turns out, the K31 action is strong enough; so much so that I should be able to safely reload my ammo to the level of the ammo built for more modern rifle actions.

It turns out that the Hammerli company has used the K31 receiver to offer rifles in calibers up to 300 H&H. On the Swiss-Rifle forum there's a guy who uploaded copies of the original advertisements from Hammerli. Some of the other calibers that have been chambered using this action are the 308 Winchester, 3006, 300 Win Mag and others I can't recall right now. If the pressures are within the maximum pressures of the most powerful of these, I suppose they're within the safety margin of this action. I would suggest doing additional research just to verify this before undertaking such a re-chambering though.

Incidentally; conversions like the 300 Win Mag and the 300 H&H rendered this action a single shot rifle due to the length of the cartridges.

HollowPoint

[Der Gebirgsjager]

A very interesting project. I doubt if the receiver started as a casting. The casting technology wasn't advanced enough to permit it during that time period. Cutting the cam surfaces seems to be the challenge. The Swiss did it, so it can be done. Just reading between the lines I gather that you have a lathe. Do you have a mill? Good photos!

[Cap'n Morgan]

Looking forward to see this project finished. Excellent choice in caliber...

If you can't wait for the metric thread gauge to show up; just screw the barrel into the receiver, unscrew it exactly five (or six, or seven) turns, measure the gap & multiply with 25.4, then divide with the number of turns - and you have the metric pitch.

The receiver was probably die forged close to size to minimize machining, but there was no doubt an awful lot of handwork and filing involved.