Adding a shoulder?

Discussion in 'Gunsmithing' started by Tgunz64, Nov 28, 2019.


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  1. 112Savage

    112Savage Well-Known Member

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    Several manufacturers contour light barrels to have a “bell” or step up in diameter right before the threads start (Barrett field craft). I have seen where a gunsmith can thread the rifle further back and place a “permanent” collar which will make an effective larger diameter shoulder for the brake or can to sit against. This collar is threaded with very little relief so that it is tight and then rockset into place. For light weight barrels with ample bore wall thickness but narrow shoulders, this may be an option.
     
  2. swat

    swat Well-Known Member

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    it all come's down to barrel wall thickness. i have seen some bad strikes with suppressor's that were on thin barrels. seen one break off at the back of the thread's. if you have to use this barrel, cut it back to at least .625. more is always better.
     
  3. 112Savage

    112Savage Well-Known Member

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    Everyone unnecessarily worries about barrel wall thickness and flaring of the crown portion of the barrel. I have a 9.3X62 Zastava M70 that has a muzzle diameter of 0.565". So with a 0.366" bore that leaves 0.998" wall thickness. Now some real smart people will say that 9.3X62 isn't a high pressure cartridge, but even without modern pressure that's a lot of mass going through the barrel and the factory thought it had sufficient thickness. 1/2x28 is THE threading for 22 caliber barrels and is completely sufficient. The OP just needs to have a shoulder built up on his rifle.
     
  4. Tgunz64

    Tgunz64 Well-Known Member

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    Our muzzles are the same. Mine is .566. To get the .600 the companies speak of I’d be at an 18” barrel. It’s currently 22”. I dont want to go that short. I’d go to a 20”. If I had the muzzle end at 20” and measured back to the shoulder from there it’s .590. Might just forget the whole thing. Maybe have a brake installed since the gun is already at the shop. Or save the money and just have it shipped back. Live and learn right? Didn’t realize thickness was such an issue until Friday. Just figured if you had enough room for threads a mount would work.
     
  5. BountyHunter

    BountyHunter Well-Known Member

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    Guys build adapters to go from one thread pattern to another. They have shoulders. You could get one of those.
     
  6. 112Savage

    112Savage Well-Known Member

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    Just have it threaded and a shoulder added. Your wall thickness is okay you just need a shoulder adapter.
     
  7. Tgunz64

    Tgunz64 Well-Known Member

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    Know of any place that makes a good adapter?
     
  8. 112Savage

    112Savage Well-Known Member

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    Most any gunsmith should be able to do it. Call around and describe what you want.
     
  9. Tgunz64

    Tgunz64 Well-Known Member

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    My gunsmith is confident the Hellfire will still work even with a small shoulder. But said we’ll get it on their for you one way or another. Just wondering what mounts are out there. He said he knows of a couple. But still, I’ve never had work done like this before so it still makes me a little nervous.
     
  10. bigngreen

    bigngreen Well-Known Member

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    It's like a 10 min job making a shoulder from a thread protector, contouring it and cutting the shoulder square to the bore, it's not a big deal, not as big as a suppressor moving and a baffle strike!!
     
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  11. DavidleeCole

    DavidleeCole Well-Known Member

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    My gun smith helped me out one time I bought an break for my 300 weatherby mag with factory barrel and he cut about 1 1/2" off and then did the threads and screwed it on. He first told me that he was disappointed in me for not doing my homework and would not be responsible for how it turned out shooting wise mechanically it was sound but had less shoulder than recommended. He only cut it back a bit to have enough meat for the threads OD and enough meat between the threads and bore of the barrel. The rifel shot fine and was a real treat to shoot for the next 3 years while I saved money to get a new barrel. I would say use your best judgment and talk to your smith what can be done and save money while you shoot that barrel out and get one later done the road. We did use a lot of red loctite to secure the break as that was his main concern for not having enough shoulder to torque against was it working lose. It worked fine and I would do it again If i had to.
     
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  12. Tgunz64

    Tgunz64 Well-Known Member

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    Yes he also mentioned red loctite. Because of the small shoulder and guarantees it’ll stay put. He’s done other barrels with small shoulders and had no issues I guess. So we’ll see. Again he said he’ll get it to work one way or another. This place comes highly recommended by the gun shops near me. And with 8 gunsmiths on hand I’m sure they can figure it out. Again it’s my favorite gun and never having gunsmithing done before it’s still a little nerve racking. I have more confidence in him after talking with him again on Monday. So we’ll just see what happens. They are backed up so it might be 3 weeks until he gets to it.
     
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  13. Andrew Cowling

    Andrew Cowling Well-Known Member

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    I come across this quite often on clients guns.
    The picture shown is quite good. Basically the thread is cut extra long so that a thin nut or threadded washer can be screwed on tight that will become a perminant collar with perminant loktite or soft solder.
    I have done it many times. Even on a barrel at the chamber end as the near new donor barrel had a wide enough knox form for the thread but not a big enough shoulder for sufficient lock up. That rifle was a one holer at 300 metres.
     
  14. Tgunz64

    Tgunz64 Well-Known Member

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    what picture? The adco link I posted? Im sending my smith the hellfire mount well before the work starts so he can take measurements and check it all out and go from there. Worst case scenario I have it threaded and a brake matched to it or just have it shipped back as is. Then buy a new gun that will work :D
     
    Last edited: Dec 3, 2019