What barrel did I get?
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Thread: What barrel did I get?

  1. #1
    Join Date
    Dec 1969
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    sick What barrel did I get?

    TIA

    I purchased (cheap) a 7mm mauser (large ring) barrel at a swap meet yesterday. The elderly seller said it came with a large order of Israeli 308 barrels purchased years ago.

    Despite its appearance, it will not thread into the two VZ-24 actions I've tried it on. Other that looking like a long sporter barrel, it is identical to the two barrels which flank it in the pictures. Thread gauge for all barrels give s 12tpi.

    Only mark of note is "75B" and a "B" in a circle.

    Any Idea what I bought? Links to pictures below. Mystery barrel is in the middle.

    Thanks! Tony



    https://goo.gl/photos/VFQ57edDrNgHUDdb8

    https://goo.gl/photos/gPG2ScB8jabQRL7y8

  2. #2
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    Check the diameter at the threads. A Mauser "small" ring barrel has diameter of 1 inch. A Mauser "Large" ring barrel has a diameter of 1 and 1/10 inch. Most 7mm barrels were made for small ring actions. A small ring barrel will not thread into a large ring barrel. A VZ-24 is definitely a large ring action.

  3. #3
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    Thanks for responding! The barrel is 1.1". I compared it to the other two (8mm) barrels I had. They are also 1.1" The mystery barrel looks to be 24", not 21" and is thin compared to the military mauser barrels.

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  5. #4
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    Did you chase the threads? Does it just not start or does it start and stall? If it stalls, how far in does it stall? Less than one revolution says the threads are wrong. Not a lot of info here to go on.
    If you're not outraged, you're not paying attention!

  6. #5
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    It starts and stalls. I tried using a my wheeler wrench to work in on, back and forth. Others can be more or less hand fit, at least most of the way.

    What is chase threads?

    thanks! Tony

  7. #6
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    Default Mauser madness

    Brownell's and perhaps others, can supply a tap and die set for either large or small ring mausers, which can be used to correctly "size" or chase the barrel and receiver threads for a CORRECT fit. In a perfect world, the barrel threads should turn in the receiver threads with no more than hand power. Unfortunately, in the real world, due to manufacturers tolerances, this mostly does not happen and gunsmiths and their suppliers, regularly make a good part of their living correcting this problem.

  8. #7
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    smile

    I need to rent a 8mm Mauser reamer, maybe one of those places will rent me a set of chasers. Else, I can always bug my gun smith.
    Sounds like a plan!

    Thanks to all, Tony

  9. #8
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    I bet if you measure it its around 29 inches looks to be a nice 7mm barrel from a 1980 brazilian if its got the b75 and b in a circle.

  10. #9
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    Quote Originally Posted by aaron10 View Post
    I bet if you measure it its around 29 inches looks to be a nice 7mm barrel from a 1980 brazilian if its got the b75 and b in a circle.
    I have one of those...and...upon trial, some receivers it will screw right onto, and others...not even half way!!
    Tolerance stacking!

  11. #10
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    smile Gunsmith

    Thanks for responding!

    The whole length is 29", has a circle B, and 75B (not b75).

    Do you think it is commercial, or military?

    It is 26 3/4 inches from the big step/chamber, and it is very thin. Good for hunting, else, why so long and so thin?

    I emailed my smith about chasing the barrel threads. Rental is $60 with a handle and shipping.

    Thanks much!

  12. #11
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    Its military the brazil 1908`s have a smaller diameter rear site base unlike the 8mm cz- 24 barrels , that barrel contour is the same as what you`ll find on the 1909 argentines as well. They both are around 29 and a 1/8th inches for the 1908 and 1909 longrifles.

  13. #12
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    The barrel form looks like what I saw during a quick internet search. This barrel is as long as my 30-40 Krag......... Me thinks it will need a cut and crown as well. Else, as is silhouette rifle?

  14. #13
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    Forgot, brief internet search yielded 1908 Brazilian Mauser couture. That first step is distinctive, as well as the length.

  15. #14
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    Before you rent the chasers, try the old lapping compound trick. Coat the threads with lapping compound, I use A grit, and start screwing and unscrewing the barrel. It should go a little further each repetition. Put fresh compound on every once and a while. Hopefully, it will screw in completely in an hour or so. Be sure to clean all the grit out of the threads when finished.

  16. #15
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    Be careful threading dry threads in to dry threads.I have seen gauling occur.You run the male thread in just fine,and it wont come back out....EVER. Using force will get it back out...sans threads.A little antisieze is cheap insurance you will get it back out of the receiver.

  17. #16
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    Your actions are threaded for 98 type Mauser barrels with a metric pitch close to but not exactly 12 tpi. and they are a 55 degree v angle instead of the common US 60 degrees. They usually fit but you might check the threads.
    211 BC: I swear by Jupiter Optimus Maximus .... in the army of the consul Gnaeus Fulvius Centumalus Maximus and for 10 miles around it I will not steal anything worth more than a denarius in any one day.

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  18. #17
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    As Shooterike and Racepres have said, it's a stacking tolerance thing. Anyone who has rebarreld more than one Mauser has probably run into this.
    The actions and barrels were made in many different factories with different tooling in different countries under different QA tolerances over most of a century.
    You don't have unique threads on either the barrel nor the receiver. You can use a tap and die to chase the threads or try the grinding compound method. But as Irishsteve says definitely don't force the barrel without lubrication or it will gall and stick. That's very inconvenient and quite upsetting.
    The tightness of the threads doesn't hold the barrel in place, the seating of the barrel face against the "C" or "H" ring does. You don't want to force the barrel into the receiver.
    How many psi in a CUP?

  19. #18
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    barrel vise and a proper receiver wrench... Threads are crush fit (besides the shoulder) in Mausers - so used barrel had entirely different dynamic when threaded into a different receiver.







  20. #19
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    I suggest you buy a small three square fine file,with sharp edges and carefully chase the thread with that.Lot cheaper than hiring tools.I know the angle is a bit out,but you can live with that.If you are a perfectionist,procure a thread repair file,which will be somewhat dearer,but will have 55deg section.You can also get a wide selection of toolmakers and diesinkers files with all sorts of angles on the edges.Incidentally,in the distant past,when i was young,chasers were always used for fitting barrels,but used with a lathe.I make my own chasers now by cutting old threading dies in half,and using a clamp in holder.Chasers are always used freehand,and are a lot quicker than multiple threading passes.Regards John.

  21. #20
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    I bought a 7mm barrel that was Israeli made about 15 years ago. It was in the white like that and had the steps machined into it. If I remember correctly, it was about 19 1/2 " long. I don't remember if it had markings at the breech end, but it was stamped "IMI" up by the muzzle. I don't know what Mauser it was supposed to fit because I reworked it for an Arisaka action. I still have it. It is absolutely the most accurate carbine length deer rifle I have ever owned. Either I just got lucky, or those Israelis can really whip up a barrel.

  22. #21
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    If you have a 29 + inch 7x57 barrel you might consider selling it to a long range shooter. Those barrels are in high demand and you could sell and get what you want.

  23. #22
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    Quote Originally Posted by jjk308 View Post
    Your actions are threaded for 98 type Mauser barrels with a metric pitch close to but not exactly 12 tpi. and they are a 55 degree v angle instead of the common US 60 degrees. They usually fit but you might check the threads.
    A metric pitch close to but not exactly 12 TPI? Hmm, you mean a metric pitch of 2.116mm? Cuz that's what 12 TPI translates to. Coincidentally, thats what the blue prints for the 1909 Argentine show. So, they're threaded M28x2.116 metric or 1.10"x12 TPI. And yes, they're a Whitworth form 55 degree thread.

  24. #23
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    I've researched Mauser thread pitch and form and have come up with:
    1. It is an obsolete, pre 20th Century Metric thread - some old Mausers do not measure to exactly 12 t.p.i. BTW on the T-45 jet trainer program the spec said it was metric and we found there were several metric conventions for fasteners and metal gauges!
    2. It is 12 t.p.i. because Mauser used either British or American machinery.
    I have no idea which is correct. In either case 12 t.p.i. is universally agreed on as working OK. The thread form is, however, Whitworth, of 55 degrees, not the common 60 degrees.

    The only relevant "Blue Prints" would be those from Mauser, not a secondary source which would be likely to translate measurements into those for readily available tooling.
    211 BC: I swear by Jupiter Optimus Maximus .... in the army of the consul Gnaeus Fulvius Centumalus Maximus and for 10 miles around it I will not steal anything worth more than a denarius in any one day.

    2016 AD: To enhance our community's aggregate through multi-platform metrics of media synergy catalyzing integrated outcomes of macro-disciplines toward inclusive methodology paradigms generating positive algorithms of unwavering commitment to our children, the flag, and God.

  25. #24
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    The blueprints I referenced were DWM blueprints for the 1909, thus I believe they are relevant. The Brits were supplying machine tools in that time period, thus the Inch thread pitch and Whitworth forms on the threads.

    We have verified that the threads are indeed 12 TPI on an optical comparator.
    Last edited by z1r; 04-29-2017 at 05:25 PM.

  26. #25
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    12 TPI 60degree thread works fine.

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