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Thread: rebore a rifle barrel

  1. #1
    mobile_bob is offline Stainless
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    Default rebore a rifle barrel

    this is a muzzle loader, and i want to rebore to a larger caliber

    can i use one of those eldorado v grooved rifle bits to rebore an existing hole in a barrel?

    yes i have a lathe and have bored barrels in the past with a fabricated twist drill to to the deal, but wonder if the carbide tipped
    rifle bit would be a better way to go.

    or are they only to be used for the original hole? meaning will the wander off when reboring an existing bore?

    thanks
    bob g

  2. #2
    ronan is offline Cast Iron
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    You could drill the larger hole with a piloted drill bit with the pilot section the same diameter as the old rifling, i don't know how you would re-rifle the newly bored barrel though.

  3. #3
    Anvil Jenkins is offline Hot Rolled
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    Quote Originally Posted by mobile_bob View Post
    this is a muzzle loader, and i want to rebore to a larger caliber

    can i use one of those eldorado v grooved rifle bits to rebore an existing hole in a barrel?

    yes i have a lathe and have bored barrels in the past with a fabricated twist drill to to the deal, but wonder if the carbide tipped
    rifle bit would be a better way to go.

    or are they only to be used for the original hole? meaning will the wander off when reboring an existing bore?

    thanks
    bob g
    I THINK you are asking about a gundrill ?? I did a google on the term "eldorado v grooved rifle bits"....and it sort of led me to gundrills.

    Gundrills are designed to drill into solid metal, running them into a pre existing hole IMHO would not work out so well, for a variety of reasons, one being they are designed for high pressure through oiling, and an existing hole would allow the oil to escape forward.

    In another thread we were talking about rifle barrels in general, and they sell the cheapest blanks for about twice what the bar stock would cost me from speedy metals, so IMHO it will be cheapest and best for you to buy an off the shelf blank from say Midway..then open up whatever rifled bore is in there to install your liner for the ML barrel...but that is just my opinion :-).

    There is no easy/good way for the average person to cut their own rifling..........

    Bill
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  4. #4
    trevj is offline Stainless
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    Quote Originally Posted by mobile_bob View Post
    this is a muzzle loader, and i want to rebore to a larger caliber

    can i use one of those eldorado v grooved rifle bits to rebore an existing hole in a barrel?

    yes i have a lathe and have bored barrels in the past with a fabricated twist drill to to the deal, but wonder if the carbide tipped
    rifle bit would be a better way to go.

    or are they only to be used for the original hole? meaning will the wander off when reboring an existing bore?

    thanks
    bob g
    Gundrills are not for re-drilling holes. My understanding is that the shanks are reliant upon the lubrication from the cutting oil being pushed back up along the vee groove, as it carries the chips out. Hard to do that when dealing with an open end on the barrel.

    You really want a drawtube mounted reamer or, if you are wanting to remove a bunch of material, a piloted drill, I think. Then the reamer. Then the rifling cutter or button.

    Pretty much certain that all the makers of gun drills also will sell you reamers for that.

    Cheers
    Trev

  5. #5
    mobile_bob is offline Stainless
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    ok guys, thanks for the input so far

    i understand the oiling situation, and figured on plugging the off end of the barrel so that the oil would then be forced to return back down the v groove.

    my question is this
    will the v groove rifling bit self center and cut relatively true down the existing hole?

    as for rifling, that hurdle happens after getting the hole to size and reamed.
    one step at a time, as they say.

    bob g

  6. #6
    ronan is offline Cast Iron
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    Could you drill out the barrel and fit a liner seeing as its a muzzle loader ?

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    Quote Originally Posted by mobile_bob View Post
    my question is this
    will the v groove rifling bit self center and cut relatively true down the existing hole?

    bob g
    I would expect the bit to chip where the existing rifling will hammer on its edge min 4 times per revolution. It will most probably wander sideways upon start due to the asymmetrical ground tip as well.

    re. one step at a time..

    All the rifling methods used, require the rifling tooling to exit the barrel.

    Although it might be fun to try it.. I think the most economic choice would be to buy a new barrel blank and start from there.

  8. #8
    mobile_bob is offline Stainless
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    the whole idea behind this project is to gain the experience and the tooling needed to start from scratch to build a muzzle loader, from a piece of round stock, drilling, reaming, burnishing, and rifling.

    yes i know it would be easier to buy a barrel from a barrel maker, however getting the caliber i am after ain't gonna happen, nor would the diameter of the barrel be common in most shops.

    fwiw, i decided to make a long bit yesterday, it uses a screw on counterbore bit such as used on microstop counterbore tools, it has a pilot that fits the original bore of my tube and so far is working quite well albeit a slow in/out process to clear chips... the size of the bored hole is still sufficiently undersized to require a final bore pass to get it to near enough for a reamer pass or two.

    much like the rational a mountain climber will state when asked why he climbs the mountain
    my answer on this project is similar

    "because its there" or rather in my case "because i want to do it"

    thanks
    bob g
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  9. #9
    trevj is offline Stainless
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    You got any toolpost grinding or tool and cutter grinding capability?

    The way I see it, the old tech means of drilling and reaming barrels (1800's technology) would work fine, if slow, but these days we have a considerable selection of decent HSS reamers available to start with, to grind in to custom tools. Way easier to adapt a tool than build from scratch!

    Not a big deal to mount a reamer on a tube, and grind a nice pilot on it, so it follows the existing bore. Use a coolant flush to push the chips ahead of it as it gets fed down the barrel. Easy enough.

    Rifling, though, the more I learn about the stuff, the more inclined I am to buy a barrel from someone else. I figure I can do it, I just don't figure I ever will.

    Cheers
    Trev

  10. #10
    mobile_bob is offline Stainless
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    well curiosity got the better of me and i setup the carbide rifle bit in the lathe, using a milling attachment to secure the bit and a steady rest to maintain the bit for entry into the hole.

    yes a bit tricky to get started, but once everything was put into near perfect alignment, it started right in, i used the old in and out with a brush and oil, but soon got tired of that.

    rigged up a coolant pump to the bit, plugged the other end of the barrel and things went really smoothly, i quit at about 12 inches and removed the barrel to take a look and see if the new hole was reasonably tracking with the original hole... all looks well indeed

    the bit sure does make a nice clean and very smooth walled hole!

    measured and found i will have about .010" to ream to final size which isn't bad in my opinion

    it appears the spinning barrel keeps the bit forced to center and it tracks very well, at least so far.

    thanks guys for the input, this project gives one a real appreciation for both the old dudes back in the early days of barrel drilling
    and also for the high tech solutions that are used today.

    i would like to think maybe i am somewhere between the two? probably closer to those guys of the mid 1800's

    bob g

  11. #11
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    Quote Originally Posted by mobile_bob View Post
    ... getting the caliber i am after ain't gonna happen, nor would the diameter of the barrel be common in most shops.
    Quite a few barrel shops in the USA will make any OD, any caliber, any twist that you want. I understand that you want to do it yourself but the "pay & play" option is there if you need it.

  12. #12
    Alpacca Fortyfive is offline Stainless
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    - Will a gundrill ream an existing bore?

    no.

    They're made to be started in a hole or bushing which is within a micron or two (micron = 1/1,000 mm = 1/25,400 inch) of the cutting diameter of the drill

    the starting hole or bush stabilizes the drill until it can stabilize itself as it cuts into solid.

    The forces from cutting an already existing bore will screw up the stability of the drill, and likely break it.

    just plugging the end of the barrel will result in the bore ahead of the drill packing up with cuttings, which will definitely break the drill.

    As others have said, its a job for a piloted drill or a piloted reamer - the (?only) two good mid 20th century gunsmithing books;

    Vickery, and,
    Howe vols 1 & 2

    cover the process in some detail. They're up as .pdf files on some of the download sites - a search engine will find them.

    avoid any book with the name Harold Hoffman on it - he doesn't explain the subject very well, and he doesn't cite sources of his info ( vickery and howe - the typos are Hoffman's contribution)


    Gun drills are good at what they were designed for - drilling deep holes in solid. If you're interested in them, there are some good refs available as downloads on Viktor Astakhov's site.

  13. #13
    mobile_bob is offline Stainless
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    thanks guys

    as they say an education is expensive, and so far this question has cost me a 60 buck piece of steel,, yes the bit took off and went off center a bit further than i could salvage in the tapering of the barrel process

    i did learn a few things in the process

    1. plugging the end of the barrel does not result in swarf packing ahead in the hole, it comes right out with the fluid no problem

    2. the bit is very robust, and the tip is nearly indestructible, believe me i tried!

    3. the bit provided an excellent finish which i was happy with.

    4. my bit holder was a real problem, keeping everything plumb was a real issue, and likely added to the problem of the bit taking off center.

    so i have set the bit aside for now and went back to the piloted counterbore, having made up the long shaft, drilled and threaded it to accept screw in counterbores, and then grinding to diameter a counterbore to do the drilling with.

    i think with a pilot there is no way that the bit is going to go anywhere but down the barrel.

    thanks for the tips on the books

    i managed to find a first edition box set (Howe vol 1 and 2 circa 1934) signed "best wishes from the author" with his signature
    lots of good info contained in them.

    i will look for "vickery" and see what i can come up with.

    thanks again
    bob g

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