Trying to change out barrels in a M 12 (12 ga). There must be a special tool to do that--correct? Thanks, Gil

That's a big help, Larry. The vises and wrenches can probably be acquired for less than $500.00. How about some hints about how to do it without these expensive items?

I’m my limited experience (a total of 2 complete take downs of the Model 12), this is the only way to correctly remove the barrel from the extension without marring it up. I’m sure there’s other ways. I don’t know what those ways are. An old timer suggested putting the barrel in a lead lined vise, wrapping the extension with leather and using a big pipe wrench or 15” crescent to turn it. I didn’t want to try it that way.
Those barrels are screwed in so damn tight to that extension sometimes it’s a pita even when using the proper tools. If I ever re-do another model 12 anytime soon…I’ll just leave the extension and barrel coupled together while polishing.

Easier to buy a second extension and add to second barrel I’ve found. That way you keep the original, original. They pop up on EBay often.

I made my barrel vice out of a hydraulic press and machined an action wrench I also made a flat wrench out of .5 thick flat steel 2 bolts it's 18 inches long it's 1.5 inches wide

I use a home made wrench to latch onto the extension to remove and re-install them.
You need a bbl vise as well to securely hold the bbl w/o it turning,,that's a given for any of this work.
Wooden or lead 'jaws' work the best for me for that along with rosin.
Leave some clearance around a vent or solid rib just in case the bbl decides to slip while working on it.


The wrench shown is a simple piece of flat steel about 1" accross x 3/16 thick(?). It's about 14" long.
It's what it was as scrap when I picked it up to make the wrench.

The upper plug is a fixed position.
That is for the chamber plug.
It is easily removeable with the bolt screwed thru the handle.
Different size chamber plug for what ever gauge/chamber bbl you are working on.

A slot is milled below the fixed chamber plug position to accept a plug that can be adjusted the length of the slot.
This plug will be adjusted to fit into the magazine tube hole position reletive to the chamber of the bbl extension you are working on.

The plug is simply screwed onto a bolt from one side and tightened in position.
The diameter of that plug is made to fit closely into the inside of the magazine tube opening on the bbl extension you are working on.

You make different size magazine tube plugs for the different size frames needed.
You use the one wrench on all gauges with different chamber and magazine plugs
Works on 410 also on the Win 42.

Insert the upper chamber plug into the chamber of the bbl and the lower plug into the magazine hole in the extension.
Use the leverage of the handle to unscrew the extension,,the entire wrench pivots around the plug in the chamber.
Sometimes a tap in the end of the handle with a lead hammer breaks them free if stubborn.


I've used this for years when called on to dismantle a 12 or 42 bbl extension. Not a big M12 person, so the # worked over isn't a big one. But the system never failed and never damaged an extension.

Trying to simply wrench one off with an open end wrench of sorts will generally put a kink in the extension in that weak action rod cut...
In reality, most any work can be done w/o removing the extension anyway.

Kutter, I understand that most work can be done without removing the extension. I am not interested in refinishing. However, I would like to remove the barrel from the extension and install another barrel on the same extension. These instructions and tools and fixtures are way more than most of us can take. Another question, can we expect to install "another" barrel on an extension and have it index at the same place. If it doesn't tighten up at the same index mark, what is the solution?

These are about the simplest the tools for this job,,working on the M12 bbl extension.
If you try and go any simpler than this, you will more than likely crush or otherwise damage the bbl and bend the bbl extension.


If the old bbl extension over tightens when installed onto another bbl.
You can punch the threads on the bbl forward a slight amt. That makes the take-up of the threads a little quicker (lack of a better word)
and the extension will thread back on and come up to about the 9 oclock position in contact with the bbl shoulder.
Then the wrench will be needed to torque it into position the rest of the way.

This same method is often used to tighten a TD joint on some rifles like Winchester TD guns.
Not meant for repeated disassembly/reassembly. Meant to be assembled and left that way.
I've seen it used to tighten a bbl up on a bolt action rifle as well that is over clocked a bit.

Use a small face flat 'drift' and a hammer. Place the face of the drift against the side of the V of the thread and lightly and evenly punch the thread TOWARDS the muzzle of the bbl.
Start at one end of the thread on the bbl and go all the way around the entire thread and all the way to the end of the thread.
It doesn't tke all that long. But the threads are small and fine. Take the time to do it right and don't mess the threads up.

You are displacing the V a very few .000 forward. That draws the part being screwed into place (the bbl extension in this case) onto the bbl 'quicker than the orig threads.
As a result, the extension comes up tighter to the bbl shoulder quicker (that 9 oclock position) and then needs the wrench torque to really tighten up to the 12Oclock for you.

Many around now would just use LockTite or similar I assume and save the work. But I really don't care for the stuff.


If the old extension comes up way short of where you want it to be, you can either take small amts off of the bbl shoulder that it sits against.
.. a safe edge file works well. I use a sharpie pen as high spot marker to see where I need to file.

Or you can simply remove matrl from the front side of the bbl extension. Again Sharpie mark the front of the extension and screw the bbl in tight. Remove the bbl and file the spots down where the marker is rubbed off brite (high spots)
Keep watch as you get closer to the 12oclock position where you want the bbl to end up and leave some 'crush factor' turning distance for the wrench to tighten the assembly together.
Don't go by the old witness marks.

I like Kutter's tool.

What I did for a wrench (before I started acquiring metal working tools) was simply cut the exact right shape oval hole in a sturdy piece of 1x6 x 24" (or so) hardwood. Then use it like Larry's adjustable wrench. You'll eventually split it but it only takes a few minutes to make. This tool would be silly for a real smith but you'll probably only need it twice.

Now to get to the basic question. Who is in the business of doing the barrel exchange so we don't have to do it ourselves? I have a drawer full of Model 12 and 42 barrels that I would like to install on good guns that have been cut or had choke devices installed.

Nu line guns used to work on M-12's there new website isn't showing any gunsmithing services. Just under construction.