I have been using a big clunky and cumbersome barrel vice I built way back in the 70s. Think two big chunks of 2" x 3" bar stock and you will have a pretty good picture. I was so impressed with guntech's setup that I decided to copy it with one slight modification. I thought I would post it here on the chance it might help members who are thinking of building one, or have a suitably equipped shop build one. My total material cost was under $50.00 and that included enough material for about 15 inserts. It's sometimes better to buy an off-cut than pay the cutting charge.
The following is presented with guntech's kind permission.
Let me start off by saying I consider myself a rank amateur in the gunsmithing and machining departments. The sketch is a shop drawing that I dolled up a bit for this post and, yes, I know it makes for a pretty lousy perspective drawing.
The clamp blocks started out as a piece of 1 1/2" x 2" hot rolled that I squared and trued up on the milling machine with a fly cutter. Cold rolled would have been just as good. This is a tool, not a work of art. The ends are as they came off the bandsaw and I just hit the faces with a file to knock off the high spots left by the fly cutter. After boring and threading all the bolt holes and making a temporary 1/4" x 1 1/2" x 6 1/2" steel spacer, it was all bolted together and chucked in the lathe for boring the hole for the inserts.
I chose to go with 1 3/4" diameter aluminium inserts instead of 1 1/2" steel. I expect to make an insert for the Ross Mk III at some point and I felt 1 1/2" inserts might be a little on the small side. The raw material is 1 3/4" diameter aluminium bar stock. You may have noticed the bored hole in the clamp blocks is 1.750" + 0.000" and -0.005". It's easy to remove a little from the diameter of the insert stock, but it would be a pain to have to shim the inserts right out of the gate The inserts are 1 1/2" long. I pre-bored three at a time and then cut them to length. Three were pre-bored to 1" and three were bored to 7/8", just in case.
Finish boring was done on the lathe. Two sets are shown. The set for the Lee Enfield No. 1 is just a round hole bored with a 1 1/2 degree taper, give or take. The set for the MLM/LEC is a little more complicated in that it is a tapered round hole with a 1 degree taper, with additional stock removed to accommodate the raised portion of the knoxform. That was done on the milling machine before the insert was split.
Here's a tip for getting the correct taper. Lightly chuck a barrel up in the lathe with a dead centre in the chamber. Don't turn the lathe on and I would unplug it or hit the emergency shutdown, just to be safe. Indicate your compound angle off the knoxform, or whatever area is to be clamped and Bob's your uncle. Once the interior of the insert is fully formed, slice it in two and you are ready to go. I find turpentine saturated with rosin and painted on the inside of the clamp pad works well to prevent slippage.
Hope this helps someone
Thanks go to guntech