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Thread: Wall thickness on a smoothbore question

  1. #1
    Boolit Master RU shooter's Avatar
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    Wall thickness on a smoothbore question

    My plan is make a smoothbore using a modern 20 ga shotgun barrel . I know these are made from stronger steel than most regular smooth bore black powder barrels from colerain and others . What's a minimum safe wall thickness ? .180? I am planning just a simple drilled vent no liner .

    Tim
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  2. #2
    Boolit Master pietro's Avatar
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    .

    The barrel wall would need to be plenty thick enough to give the breechplug sufficient thread depth, with a safety margin, so it won't blow out/back when shot.

    .
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  3. #3
    Boolit Master
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    I would use the chamber area as im betting this is a bunch thicker and enough meat to get a whole thread depth for the nipple. The rest should be thick enough and plenty strong for any black powder load. (( you are going to use black powder eh?))
    WHEN ALL IS SAID AND DONE...MORE WILL BE SAID THEN DONE

  4. #4
    Boolit Master
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    The safety issue of having the breech area thick enough for threads, etc. has already been addressed and all of that is really common sense. That said, I had a very nice barrel that was about a 28 gauge IIRC that was made out of a "modern" single barrel. They utilized the thicker chamber area for the breaching of the barrel. I would consider it to be a "lightweight" barrel as I don't think I would have wanted to shoot real heavy loads from it. Whoever did the work put a flat on the side for the lock to fit against - it was kind of neat. I never got around to doing anything with it so I sold it - now I wished I hadn't.

    I have a 42" 20 bore barrel (.620) on my Fusil de Chasse trade gun. It of course has a heavier breech area for he same above reasons mentioned, but I have always considered it a lightweight barrel. I believe mine is a collegian barrel. I've never been one to "over load" a muzzleloader of any kind in the 50 + years I've been shooting. My Fusil does well though with a .600 or .610 patched ball and 60 grains of FFG Goex and it shoots well with a shot load too - well enough that I've taken pheasant and even a duck or two at good distances years ago.

    If you can find a modern barrel with a thick enough breech area to do the job, I think you'd end up with a nice gun. Good luck - sounds like a fun project!

  5. #5
    Boolit Master

    rfd's Avatar
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    digital calipered my .62's colrain barrel - the bore is .616" and the wall thickness is .102" - all at the muzzle.

  6. #6
    Boolit Master
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    If I remember correctly on all the muzzle loaders I have put together the breech plug has a seating surface machined into the barrel. That does the sealing and the threads are there to hold the plug tightly against the interior seat of the barrel. I put together a 45 caliber slug gun last year and the breech plug was not installed you but there were some machinist blue marks on both barrel and plug at the seating surface but most all was rubbed off.

    I have read that 50 caliber M2 barrels are used quite a lot for 50 caliber muzzle loaders?
    John

  7. #7
    Boolit Master RU shooter's Avatar
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    Quote Originally Posted by bigted View Post
    I would use the chamber area as im betting this is a bunch thicker and enough meat to get a whole thread depth for the nipple. The rest should be thick enough and plenty strong for any black powder load. (( you are going to use black powder eh?))
    Yes I am planning on using the chamber are . But the twist I want to do to it was surface grind that thicker part of the barrel octagon shaped instead of leaving it round . Also there will be no nipple or vent liner to worry about threading in just plan on a simple drilled vent . An yes holy black only
    If you find yourself in a fair fight, your tactics suck!

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check