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Thread: Converting a long Mauser 98 barrel to a K98k barrel

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    Converting a long Mauser 98 barrel to a K98k barrel

    So I'm working on a franked-rifle project because I find that sort of thing fun. In this case, we're starting with an orphan M1909 Argentineicon Mauser barrel that had a bulged muzzle. Someone clearly removed this barrel and re-purposed the action, I have no idea if it got the ringed muzzle in service or through abuse here in Canadaicon. The bore is otherwise pretty good. For a project, I'm going to build a German Kar98kicon pattern rifle that externally will look like an issue K98k, but that will be chambered in 7.65x53 Argentine. Why? Well, because I can, and I like the caliber. I have dies, brass, etc. already as well. I also have most of the parts on-hand.

    I have a take off K98k 8mm barrel with a poor bore that I'm using for reference. By poor, I mean heavily pitted, counter-bored, and generally awful, but that's OK, we're just pulling dimensions off it.

    So right away, there are some things that we need to fix:

    1) An Argentine 1909 barrel is 29.13" long while a K98k barrel is only 23.62" long.
    2) A K98k Barrel has a .900" journal ahead of the chamber that the rear sight base is soldered to. An argentine barrel, on the other hand, is 0.760" in the same area as the argentine sight base is smaller in diameter.
    3) The end of the chamber area on a K98k is a sharp corner, on an argentine barrel, it's radiused.
    4) The Argentine barrel necks down less quickly, so near the muzzle we will need to reduce the diameter to match a K98k barrel contour.

    Here's an example comparing the rear sight area of both barrels after the sights are sweated off (Argentine on top):


    Note that the argentine barrel is thinner. I've already cleaned the ruling off in prep to solder on a collar to increase the diameter. Also, I already turned the the front of the chamber area at the step to get rid of the radius there. The sleeve will now fit flush and we can re-machine a nice, sharp step like a K98k barrel.

    In this photo, you'll see an old piece of shotgun 12 gauge barrel I've already bored out to .76" inner diameter. I took this photo before machining off the radius at the barrel step, you can sorta make it out:



    Next, I re-tinned the argentine journal. It was not tinned in many areas, just where the rear sight base made contact. I also tinned it over a longer surface.



    I also tinned the inner diameter of the sleeve. You'll notice the sleeve is now machined down closer to final dimension. It's still about 10 thou too big everywhere and will be machined to final size on the barrel, in case it solders on slightly off centre.



    Now it's soldered on and needs to cool. If you do this project, the sleeve should not go on all the way when cold once tinned. If it does, you machined the ID too big. It should start on, but it should only slide home once you heat it enough that the two tinned surfaces liquify. Use a thin coat of flux on the barrel shank to help the two surfaces fuse. I add more lead solder to the top until I see it come out the seam at the bottom. I then let the bottom cool a little and add a bit more at the top to fill any remaining joint gaps. It will get cleaned up later when we machine the sleeve to final dimension.



    Set up for soldering:



    You'll notice the sleeve heat blued. No big deal. These barrels are not hardened anyhow and the germans heated them with Oxy Acetylene to install the rear sight bases at the factory. It will be in the white again once we turn it to size.

    I next machined in the shoulder and turned the journal to final dimensions. Next I need to machine the journal to length and add a small journal that matches the handguard inner diameter.



    Next the barrel is re-countoured and the old bluing sanded off. I need to install it on a receiver to index the sight bases.



    I should have took a photo, but the foremost narrow section of the barrel is freshly cut/contoured on the lathe. On a long Mauser barrel, the reduced diameter happens further out than where a K98k barrel ends.

    The barrel is next installed on my VZ24 action, and the sights were soldered on. Also, the set screw divots are drilled in the barrel and the screws installed. Sorry for the lack of pics doing the work, I had to go to my buddy's shop as he has a nice OA torch, which is better for precise soldering of the sight bases, which need to be indexed with parallel bars. Had my hands too full to take the pics.



    Before I cleaned up the solder overflow.



    Front sight before cleanup:



    VZ24 bolt handle bent to close approximation of military K98k bent bolt profile (before cleanup). I don't do these myself. I go to Gunco in Ottawa as Jason has the right jig and the right torch to spot-heat the bolt root to do this bend without too much heat getting over into the bolt body. I don't recommend a bolt bend as a do-it-yourself job. Go see a gunsmith who owns the right jig and torch. The jig is too expensive to buy for the few times I do this.



    The receiver I used. note I changed the 4 scallop VZ24 action screws for 3 scallop K98k screws. Apart from markings, these receivers are identical to WW2 German receivers and are really well made. I scrapped a scrubbed Romanian RC VZ24 for this action (yes, I know, someone will be terribly upset, but I couldn't locate a nice sporterized action).



    Clearly marked so nobody tries to shoot .308 or 8mm in this rifle. That would not be a great idea.



    Bolt re-numbered at the root, as the electro-penciled SN on the RC bolt was destroyed when I sanded the scale off the bolt handle post-bend.



    And a complete shot of progress to date. I already filed and then sanded off the solder overflow and finished the sight bases to 180 grit with emery paper wrapped around a file.



    Next up, I need to prep the part of the receiver that will be proud of the stock so that when I re-blued the barrelled action, it will come out OK and not look cloudy and stippled like an RC dip job. I used hot caustic bluing, though rust bluing could also be used. I'm not a fan of any of the cold bluing methods.
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    Last edited by Claven2; 06-25-2016 at 10:17 AM.
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    Quote Originally Posted by Claven2 View Post
    I used hot caustic bluing, though rust bluing could also be used. I'm not a fan of any of the cold bluing methods.
    I completely agree...for this one I'd want the bluing tank. I'd have bead blasted first to make sure all lead is gone from exterior and then polished...
    Regards, Jim

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    Quote Originally Posted by browningautorifleicon View Post
    I completely agree...for this one I'd want the bluing tank. I'd have bead blasted first to make sure all lead is gone from exterior and then polished...
    I'm going to cold blue it tonight to check for solder, then polish back to bright metal.

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    I forgot about that...
    Regards, Jim

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    ok, just checked it. There was one small spot remaining on the front sight. It's polished back to metal now though. Should be good to go for bluing, now I just need to wait for my buddy with tanks to accumulate enough stuff to do a run.

    That, and find a decent laminate buttstock to go with the handguard and hardware I already have.

    And I may also convert to it to a SSR sniper lookalike - still debating that.
    Союз нерушимый республик свободных Сплотила навеки Великая Русь. Да здравствует созданный волей народов Единый, могучий Советский Союз!

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    It would look good parkerized to I bet. Here's a rusty old 1940 Berlin-Lubecker Brian Dickicon did for me recently. It's really pitted so blueing wasn't an option.

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    As an engineer I find these builds fascinating to read. Looks great

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