Replacing 39(A,M,D) Barrel and indexing - Page 3
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Thread: Replacing 39(A,M,D) Barrel and indexing



  1. #21
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    Bandit,I did not notice it had an octagon barre,good luck Slackdaddy...
    What this country needs is a department of common sense! The tree of liberty would be a great place for hang mans ropes!
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  2. #22
    Gun Wizard
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    For what it is worth I have breached many ml barrels. I would take the threads per inch and devide 1 by that number. For example 3/4-16 would be 1/16=.0625". Devide that by 360.
    Take a good protractor and determine how many degrees you are off, about .00017 per degree. Remove that much from the face and shoulder of the barrel and you will be clocked. I engraved a witness mark when I did this operation.
    micmoslof and HIKayaker like this.
    Steve_In
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  3. #23
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    Slackdaddy,

    If you've been following all the posts above, very good. I'll summarize.

    Fitting a barrel can be a challenging process.

    For a new round barrel, the barrel is fitted and torqued into the receiver and indexed to a witness mark. This allows the ejector cut, the front and rear dove tails, and the magazine hanger to be mounted in the correct orientation. Since the barrel is round, it doesn't really matter where in the course of rotation it snubs up, since all cuts, marks, and inscriptions will be done later.

    For an octagonal barrel, you want the barrel to snub up tight with the top barrel flat absolutely level and parallel with the top of the receiver ( the vertical flats will also be parallel with the side of the receiver). This is proper alignment and index. If the barrel snubs up short of being aligned, then the question is "how much". If it's just a little short, then possibly it can be turned in a bit further, with proper tools. And hopefully turned in further without skewing the receiver. Otherwise, the barrel threads must be cut enough deeper (further along) the barrel to allow the barrel to be indexed (aligned) perfectly with the receiver. See the explanation by Steve In in the post above for the formula to see how much to take off.

    Since yours is a commercial barrel, it already has the extractor cut, and sight dovetails, and magazine hanger cut. This means that you need to align to a certain flat. But without assembling it, there's no way to tell whether it will index as it should until you put it together. (Make sure you use an anti galling compound on both sets of threads to help getting it apart again.) If it indexes, you're golden. If it stops short, see above.

    If it stops past, it can probably be shimmed back. I've not done this, and I don't know how it's done. Past a certain point, it will be necessary to cut the threads deeper. I don't know where that point--is more than half a rotation? Certainly before the appearance of the shim becomes obvious and objectionable.

    Once the barrel is properly indexed and torqued into the receiver, the headspace must be checked and adjusted if necessary by refacing the barrel where it meets the bolt, and also, if necessary reaming the chamber a bit deeper.

    I've never replaced a barrel. But I stayed in a Holiday Inn last night so I have a basic understanding of what it requires. I'm sure there are tricks that make it go easier. It can be a risky and involved process. If barrel adjusting is necessary--refacing, recutting threads--a lathe is needed.

    Personally, I'd run that barrel into the receiver just to see how close it comes to indexing. It may be dead on, in which case you're golden. Just check the headspace. But again it may not be. If it requires fitting, I'd just as soon have an experienced smith do it for me, rather than screwing it up myself. Something I have done many times before.

    Good luck. Let us know.
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  5. #24
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    Here is a ? for the people in the know would it be easiest to have it sleeved with less trouble
    gunscrewguy likes this.
    What this country needs is a department of common sense! The tree of liberty would be a great place for hang mans ropes!
    Team 22 Magnum # 46
    Team Old Pharts # 235
    Team Wheel gun # 74
    Team 22 bolt action # 5
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  6. #25
    Gun Wizard
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    Yes - absolutely sleeving is a good way to go with older 22's. That way you retain all your original parts.

    Also - it is difficult to find really good take off barrels.
    gunscrewguy likes this.

  7. #26
    Wrangler
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    I have installed two octagon and one round barrel new Marlin barrels from Numrich arms all three lined up near perfect with hundreds of rounds down each. Maybe I just got lucky. As for taking the barrel off be careful them things don’t come off easy at least the ones I removed didn’t.

  8. #27
    Wrangler
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    Quote Originally Posted by 39d scott View Post
    I have installed two octagon and one round barrel new Marlin barrels from Numrich arms all three lined up near perfect with hundreds of rounds down each. Maybe I just got lucky. As for taking the barrel off be careful them things don’t come off easy at least the ones I removed didn’t.
    Same here ,did an octagon on a mountie and it lined up and functioned great. The barrel came off very hard also.


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