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Thread: Re-Barreling/Re-Chambering my K31 Swiss

  1. #21
    Boolit Master
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    Quote Originally Posted by Der Gebirgsjager View Post
    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!

    I'm sure you're right about the casting. It's just that when I look at this receiver and all of its contours; both inside and outside, it's hard for me to picture exactly how they'd go about milling such a receiver. If anything, it must have taken many, many additional post-machining steps and alot of hands-on work to get it to its finished stage. The "Die Forging" mentioned by the good Cap'n Morgan might very well be the way they went about it. I'd never heard of that till just now.

    I suspect the cam surfaces in the receiver started out flat just like on most conventional rifle receivers. The Swiss must have come up with some type of jig to grind them to the desired angles.

    I do own a small Grizzly 4003-Gunsmithing lathe and a small Tormach 770 CNC mill with a forth-axis feature. Photos of this same machinery can be seen on the internet by just googling them. What I don't have is enough free-time to play around with these toys as I'd originally hoped when I took possession of them.

    I dream of being able to retire some day and playing around with these machines to my hearts content.

    HollowPoint

  2. #22
    Boolit Master
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    Quote Originally Posted by sgt.mike View Post
    NAY SAY...... OK joke over with ..
    6.5x55 Excellent choice in my opinion Hollowpoint, Very interesting project.

    Look forward to you completing this one Wish you the best of luck
    Mike
    Thanks Mike:

    I thought I'd be able to finish up the last of the work on my one-off specialty K31 Receiver-Truing-Jig but when I got to the hardware store to pick up the appropriately sized nuts and bolts for the "Spider-Setup" they only had five out of the eight nuts that I needed to get the job done. Because I have a full work schedule next week, it may not be till next Saturday till I can weld it together.

    Due to the shape of the K31 receiver, I had to cut a channel near the rear of the Jig in order to accommodate the trigger housing. If it weren't for that trigger housing hanging down from the bottom of the receiver I could just use a thick-walled 3" diameter cylindrical eight-inch section of pipe like they use for truing up Remington actions but, not so on this K31.

    Another thing is that the Drill-Rod I intended to use to act as my indexing rod was not the correct diameter. I have to return it and go with Plan-B on this part of the project. It turns out that the Bolt on my K31 has an outside diameter that is just a thousands-or-so smaller than a 55/64" Drill-Rod. The actual diameter of this particular Drill-Rod is listed as being just a hair larger than the diameter of my Bolt. I figured that because of this I could simply slide it into my Receiver for a snug fit. It didn't turn out that way. The Drill-Rod was perfectly straight but the diameter was actually the exact same diameter as the Bolt. I needed it to be the size that it was listed at in order to work. As it was it fit to loosely to get an accurate reading on the center-line of the receiver.

    I'm learning as I go along; and once I get it all done, it's not likely I'll ever need to use any of these home made specialty tool ever again; unless I were to buy another K31 somewhere down the line. I think this is an example of the "Tuition" or the cost of learning that was mentioned in one of the previous replies to this post.

    HollowPoint

  3. #23
    Boolit Master
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    I think I'm on a Roll. A temporary Roll.

    I think I'm on a roll; but that Roll ended at about two-o'clock today. My scheduled appointment showed up real late and while I was waiting I did some work on my K31 project.

    Here are a few more pics to give you all an idea what I was attempting to describe in my previous posts.

    All I need is a little more free time and I'll be able to setup this Receiver-Truing-Jig on the lathe to see what kind of run out the Receiver has. If it's less than one-thousands of an inch I'm just going to leave it as it is.

    This rifle was pretty accurate to begin with so I'm hoping for the best.

    HollowPoint

  4. #24
    Boolit Grand Master Artful's Avatar
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    Just Wow - Very Impressive project
    je suis charlie

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  5. #25
    Boolit Master
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    Thanks Artful:

    I haven't even gotten to the gunsmithing part yet, but the farther along I get, the more confident I feel about achieving success with this project.

    I might be able to set this jig up on the lathe this weekend. My long term work schedule is pretty much maxed out so the weekends will be about the only time I have to work on this dream.

    At the end of each work day, I really don't feel like doing more work. I don't want this project to become like a second job. I want to keep it in the realm of a hobby project and I want to do this right the first time so I'm taking as much time as I need to, to get it done correctly.

    I'm thinking/hoping it will be done by the end of January.

    HollowPoint

  6. #26
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    Quote Originally Posted by HollowPoint View Post
    At the end of each work day, I really don't feel like doing more work. I don't want this project to become like a second job. I want to keep it in the realm of a hobby project and I want to do this right the first time so I'm taking as much time as I need to, to get it done correctly.

    HollowPoint
    i am very familiar with this. just tinker and it will be done before you know it.
    looks super so far. i have no doubt this will end with a rifle many will envy.
    The only time you have too much fuel on board is when you're on fire.

    "There are a lot of changes when it gets below -10 below F. in everything from ammo,gun, humidity, uncontrollable shaking and the strong urge to go home. "randyrat

  7. #27
    Boolit Master
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    I was thinking the other night, "If I had all the tools and all the metal-stock and the barrel-blank ready to go and sitting on my work bench; and I didn't have to work for a living, this project would take me about a week to do." If I were to do another identical project after learning off of this one, I might be able to shave a day or two off of that time."

    But alas; I still have to work for a living. Such is life for me now.

    HollowPoint

  8. #28
    Boolit Master
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    Work really cuts into my hunting, tinkering time. I know there are people out there that make a living without working but I can't seem to do it.
    Some people live and learn but I mostly just live

  9. #29
    Boolit Buddy
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    Quote Originally Posted by HollowPoint View Post
    I was thinking the other night, "If I had all the tools and all the metal-stock and the barrel-blank ready to go and sitting on my work bench; and I didn't have to work for a living, this project would take me about a week to do." If I were to do another identical project after learning off of this one, I might be able to shave a day or two off of that time."
    HollowPoint
    the conundrum. if you did just that then it would become work and you would want to go do something else.
    i have several project that i just cant wait until i get some time to work on them until i have some time then i want to do other things then i run out of time and wonder why i didnt get anything done.
    it is the circle of life. maybe. im still not sure. the retired folks i know never have any time.
    The only time you have too much fuel on board is when you're on fire.

    "There are a lot of changes when it gets below -10 below F. in everything from ammo,gun, humidity, uncontrollable shaking and the strong urge to go home. "randyrat

  10. #30
    Boolit Master
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    Quote Originally Posted by Wolfer View Post
    Work really cuts into my hunting, tinkering time. I know there are people out there that make a living without working but I can't seem to do it.
    Yea; I know what you mean. My next door neighbors never work. They have no visible means of income and yet, just about every weekend they can come up with enough money to buy enough booze to get drunk on.

    If I were ever to retire and I had no hobbies, I think I'd go crazy; and drive everyone around me crazy as well.

    On a project related bright note:

    The metric thread-pitch-gauges I ordered last week showed up this morning. Anyone care to guess what the thread pitch is on a K31 Schmidt Ruben 7.5x55 rifle???? This information is "Holy-Grail" stuff. Before starting this project I scoured the internet in search of that very info with no luck in finding it. I even joined various forums that I wouldn't normally join just so I could ask that questions to those that one would think would possess that bit of knowledge.

    The strange thing about alot of the "Experts" on the K31 is that they either don't want to share their knowledge or their just pretending to be knowledgable in order to impress others. Frankly, I don't think there is any such thing as an expert on the K31; I mean a hands-on expert. (other than the Swiss guys who designed and made them) Most are just book-learned-experts; or, experts by literary-osmosis.

    The answer, according to my new metric thread pitch gauge is, 2.0mm per-whatever. I'm sitting here ragging on the so called, "Experts" and I have the exact answer but I don't even know how to write it down correctly. I have an excuse though. I'm bonafide ignorant about the K31 with just a pinch of knowledge.

    I'm going to have to read my lathe's users manual all over again in order to swap out the correct gears for cutting metric threads now. Oh well; it was bound to happen sooner or later.

    HollowPoint
    Last edited by HollowPoint; 12-04-2015 at 10:49 AM.

  11. #31
    Boolit Master
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    I'm ready to start squaring up my Receiver threads.

    I took alot of pics and got as far as setting up my lathe for cutting the metric receiver-threads I'll have to square up. Setting up was the easy part; actually chasing and cutting the threads will be kind of tricky for me, especially since I've never cut metric-inside threads before. I've chased imperial threads before but they were outside threads.

    I did run into some problems with my Receiver-Truing-Jig. Well, not with the jig itself but with the brass caps I was using on the ends of my Jacking-Bolts. (some call them spider bolts, some call them adjustment bolts) As I was truing up the face of the receiver, I noticed what looked like a barely perceptible wobble. It turned out that my Jacking-Bolts weren't bottoming out within those trimmed down brass 44 magnum shell casings and as I applied the slightest pressure with my cutting tool the receiver ever so slowly vibrated out of alignment. It's a good thing I caught it in time. It would have sucked if I'd screwed up my receiver without realizing it.

    Initially, I must have spent two hours working to bring that receiver into alignment. Then after it vibrated out of alignment I had to run down to the hardware store to buy some brass screws that I could use as my end-caps instead of those brass shell casings. I drilled holes into the ends of my existing Jacking-Bolts and press-fit the brass screws into them. The heads of those brass screws gave me a much more solid hold on my receiver.

    After measuring the runout on the receiver face, I found it to be .003" out of square with the axis of the receiver bore. Subsequent measurements of the other interior surfaces, including the threads showed a similar discrepancy in measurement to the squareness of the receiver's center line. I was hoping I didn't have to mess with this part of the receiver. This rifle was pretty darn accurate to begin with. It was surprising to find that it was out of square by three-thousands of an inch; although that's not really that much when you consider they were built for the most part on manual machinery.

    If I get a chance tomorrow I'll cut those threads. If I get the time I'll also edit those photos and post them so you can see what I've attempted to describe. Some of those photos were taken before I replaced those brass ends on my Jacking-Bolts. I mention this so that I don't come off like I'm telling tall tails about the obstacles I've run into thus far.

    HollowPoint

  12. #32
    Boolit Master
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    A Few More Pics--Mostly Self-Explanitory

    I've superimposed text onto the images so they make a little more sense.

  13. #33
    Boolit Master
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    Well, I got all the receiver work done. With any luck I'll be ordering my new barrel this Friday. Because of the diameter of the threaded tenon of the factory K31 barrel, the barrel I'll be ordering has to be "Special Ordered". The "Special" being a slightly larger diameter barrel blank than the typical 1.220" diameter barrel blanks sold by Shilen barrels. It takes four to six weeks for delivery of such a barrel.

    Even this slightly larger diameter barrel is still not big enough around to turn the tenon with a shoulder on it like the factory barrel. That's OK though; I never intended to redo the barrel in its factory-shoulder configuration. I'll be making my new barrel using the Savage-Barrel-Nut method. I've used this method before and it made head spacing a whole lot easier for me. Although, with the K31's tenon configuration it really won't help with the head-spacing but, I believe it will still help simplify this project some what. The only draw-back (if it can be called a draw-back) is that I have to make a specialty Barrel-Nut. That's OK too because they're not that hard to make.

    I believe there are a couple of other barrel makers who offer even larger diameter barrel blanks that would be ideal if I were re-barreling using the factory configuration but, this project is budget-driven and those other barrel maker's barrels are a whole lot more expensive. As it is, just the Shilen barrel alone costs more than what I paid for my K31.

    Before truing-up my receiver, trying to screw the original barrel into the receiver was extremely difficult. It couldn't be done by hand. Now that I've trued-up the threads and the major interior flat at the front-most part of the receiver I can just about screw in the original barrel all the way by hand. Only the last quarter-inch or so requires a more forceful grip to do so. I believe it's because there is also two additional flat surfaces just ahead of the receiver lugs that I didn't true up.

    I didn't want to take the chance of damaging or accidentally altering the lugs. Besides, the two small sections of interior flats just ahead of the receiver lugs shouldn't induce enough sideways pressure to take my new barrel off of the centerline of the axis of the receiver. It's the receiver threads and the major flat area visible in the images above that will be holding my new barrel on center.

    HollowPoint

  14. #34
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    Looks great! I just finished my action truing/ chambering fixture with the intentions of doing some similar projects here at home. Where did you get your receiver bushings? Looking for a place to buy them where they don't charge an arm and a leg. Making them wouldn't be terribly difficult, but would like to have them perfect...and hardened (and I don't have a tool post grinder). Thanks!
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  15. #35
    Boolit Master
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    Plan-B

    Sticker-Shock!

    I was on the phone with Shilen barrels today to get my new "Special-Order" barrel ordered up. Everything was going well until the gal on the other end of the line told me that this "Special-Order" barrel could only be had in stainless steel; and because it was stainless steel the total price when shipping was tacked on would be well over a hundred dollars more than originally budgeted for.

    Plan-B:

    All is not lost. I've had a "Plan-B" and a "Plan-C" in place just in case I ran into problems like this. "Plan-B" entails the making of a 4041-alloy threaded barrel-stub to match the factory K31 barrel-tenon so that I don't have to cannibalize my existing factory barrel. Into that barrel-stub will be screwed my new smaller diameter and much less expensive Chrome-Moly barrel blank. (which has now been ordered)

    What is "Plan-C" then?

    "Plan-C" would have been my last-ditch effort to salvage this project. It would have meant chopping off the existing tenon from the factory barrel and converting the existing barrel-tenon into my threaded barrel-stub. For me, this would have been the near equivalent of a failure with this project. Like I mentioned before; I didn't want to have to use my existing barrel as a means to completing this project. I wanted to keep that factory barrel unaltered just in case I ever wanted to re-install it or sell it off to recoup some of the expense of this project.

    I ordered a short length of 1-1/2" diameter 4140 alloy steel off of the fleebay auction site. The frustrating thing is that all this took place the day after I had started making the Barrel-Nut I'd be using for my original re-barreling plan. It was coming along nicely; with carefully done class-3 threads and the whole nine yards. Now I'll have to make another one cause the thread pitch will be slightly different; not quite so course as the factory 2.0mm thread pitch.

    Oh well; live and learn. This is how you get smarter the hard way. I'll post a picture of my partially completed barrel-nut just for laughs. In spite of this small setback, things are actually moving along faster than I'd expected but not so fast as to be overwhelmed by it all.

    This gives me the time to come up with the money to buy the 6.5 mm range rod and the chamber reamer I'll be needing. I'll most likely sell those off once I'm done with them just to recoup more of the cash out-lay for this project.

    Oh, and here's an off-the-wall idea; Is there anyone following this thread that has a 6.5 mm Range-Rod that would be willing to loan it to me if I offered to pay the insured shipping to and from? I have a .224 and a 30 caliber Range-Rod. If you happen to be doing a barrel project that requires one of these sizes in order to index your barrels, perhaps we can do a temporary equal-loan-swap; return them when we're done kind of thing. I'm still going through with this project wether or not anyone is interested in this possibility. I thought I'd just throw it out there.

    I'll be back.

    HollowPoint
    Last edited by HollowPoint; 12-11-2015 at 07:37 PM.

  16. #36
    Boolit Master
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    Quote Originally Posted by IllinoisCoyoteHunter View Post
    Looks great! I just finished my action truing/ chambering fixture with the intentions of doing some similar projects here at home. Where did you get your receiver bushings? Looking for a place to buy them where they don't charge an arm and a leg. Making them wouldn't be terribly difficult, but would like to have them perfect...and hardened (and I don't have a tool post grinder). Thanks!

    Thanks CoyoteHunter:

    I made the receiver bushings myself. Although they aren't professionally made, I've found that using Drill-Rod a half-inch or larger in diameter is generally straight enough to use as a truing guide. The tapered ends were turned on my lathe. As short as they are I'm more than sure they're just as true as the Drill-Rod I'm using. According to my dial indicators, my chinese metal lathe is more accurate than I am as a machinist.

    The truth is, I'm just to cheap to buy them already made up. And when you consider that this is a one-off project, chances are low that I'd ever use them again. I haven't heard of alot of DIY'ers that work on K31's so it would be hard to recoup the money one would pay for a specially made store-bought set of K31 bushings.

    Thanks for you input.

    HollowPoint

  17. #37
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    Learning The Hard Way

    Here's a couple of pics of the Barrel-Nut I wasted some time on. It turns out I won't be using it but, I'm hanging onto it just incase.

    Not pictured here is the additional spacer I had yet to make. The "Spacer" would have been sandwiched in between the Barrel-Nut and front face of the receiver. It would have given me an area of metal I could drill and tap to have used as an anchor point for the front end of my scope rail.

    My "Plan-B" Barrel-Stub-Tenon will now be acting as the anchor point for my scope mount. It too will be drilled and tapped in order to secure my scope rail. I'll have to wait till I get that far along for me to show you what I'm talking about. Right now it probably doesn't make any sense to you.

    I'll be back when I get farther along.

    HollowPoint

  18. #38
    Boolit Buddy

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    This is a very interesting threat to me. I'm a big fan of the K31 and have killed several deer with one. I understand MOST of what you are doing, but not all, since I've never done it myself. I'll be following with interest.
    INFIDEL

  19. #39
    Boolit Master
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    Very interesting thread and machining along with great photo's. Will be following this one. Frank

  20. #40
    Boolit Master
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    Thanks guys: I'm hoping that the 4140 metal I ordered shows up before mid-week next week. I may have about a day and a half of free time to at least get started on the Threaded-Tenon-Stub I was alluding to in my previous posts.

    Things are looking good right now but I don't want to get ahead of myself.

    HollowPoint

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