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-   -   mk 2 international barrel (https://www.rimfirecentral.com/forums/showthread.php?t=996729)

loiner1965 09-22-2017 12:14 AM

many thanks rick and would be interested in the thread size....so it can be done with a little thought

Yank 09-22-2017 01:07 PM

Have any of you guys replaced a MK2 barrel with another take-off? Was wondering if the indexing is likely to be close, or way off.

PS: Years ago, some guy tried to talk me into converting his Browning straight-pull .22 LR into a .25 rimfire. He wanted to do this because he once had a .25rf (probably an old Stevens falling block), and he liked it. Sometimes people get an idea in their heads, and they just can't shake it off. Oh well, it did work for Thomas Edison.

rick w. 09-22-2017 01:36 PM

My takeoff LW(light weight) BSA International barrel threads look like 16tpi to me with my gauges. When I rebarreled with the Shilen blank, I ground a piece of HSS to fit the original barrel's thread pretty closely, used magnification to help get as close as I could. The original threads are somewhat taller appearance(?), which might suggest a unique thread off the old basic 60 degree, but grinding to fit gets past that; at least for my needs. I ended up with something like a class 4 fit, and called it good.

The barrel shank is composed of three sections, the first section holds the recess for the case head, and two beveled cuts on each side of the bore for the extractor to reside in when breechblock is up.

The second section is the threading; about half of the shank length or thereabouts.

The third section is a smooth section(again about half) that fits into the front of the action with some snugness.

Then finally one has to do scope mount drill/tap if going that route. I used a Bentz reamer as it was all I had at the time, and allows most ammo to fit and shoot fine.

Kinda typical of an single shot action rebarrel, a bit more in labor than most because of all the extras setups/machining.

Once you pull your existing barrel from the rifle, the recipe to ponder is in front of you. Being across the big pond, I am sure your guys are quite familiar with the specific threading. I did not think the rebarrel was all that difficult, just have to pay attention to specifics.

I am pretty happy with my 17 HM2 rebarrel, but sometime the hornet will surface again, and onward and all of that stuff............:)

M14man 09-22-2017 06:03 PM

Reading what you wrote and trying to understand makes me realize I know nothing about gunsmithing.

tim slater 09-23-2017 02:16 AM


Originally Posted by loiner1965 (Post 9565897)
many thanks rick and would be interested in the thread size....so it can be done with a little thought

Not as a straight swap, if one is a much coarser thread. You'd have to cut off the old tenon,thread and re-chamber. Throw in proof costs, and it will be expensive unless you can do the plumbing yourself.

epoletna 09-23-2017 09:03 PM

re-barreling a Martini
I believe you'll find they're Whitworth threads. Look it up and grind yourself a tool bit for that pitch and you'll be good to go.

loiner1965 09-24-2017 12:18 PM

idea is just in my head as i never seen or read of any international conversions,
i knew if any one can do it then it would be you chaps over the big pond.
you lot have the passion and ideas to do this where as us brits tend to stick to the boring calibres lol

oldtrobh 08-09-2019 10:18 PM


Originally Posted by DoubleD (Post 9551401)
I still think the problem is the action is not big enough.

The international is quite different than Francotte.

HI All , I have converted one MK1 international to 32-20 chamber but .300 cal barrel and many 12/15's to .222 ,.223 and 6mm/223 and 32-20 with no problems what ever .. It has been said that the 12=15 can be rechambered to .30/30 but I would not consider that to be correct perhaps however the quote was meant to refer to the strength of the little action the rimless extractor is a head scratcher but it can be done several different ways just takes a lot of fiddling:) to get the extractor arm to clear the cartridge body

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