Forums.NitroExpress.com

Recently, I started to build my seventh double rifle. I want to have one that is very light-weight, and in a calibre that is legal in my immediate area, where we are not allowed to use a rifle of greater caliber than .277”. I chose the 6.5x57 Rimmed for a number of reasons. First, it’s a very fine cartridge. Second, I found a pair of arsenal-new Swedish M-38 barrels at an attractive price, and which I re-contoured and re-chambered. Third, because I already load for my Sako rifle in calibre .264 Winchester Magnum, I have a large supply of 140 grain Nosler Partition bullets in 6.5/.264 calibre.

The shotgun that I ultimately bought as the “host gun” for this project is a Zabala boxlock, extractor, in .410 bore. I want to end up with both shotgun and rifle barrels, fitted to the one action. Obviously, this entailed making a new mono-block to accept the rifle barrels. Fortunately I have a good friend who owned his own tool and die shop, and whose son took it over upon Peter’s retirement. Using the .410 barrels as a pattern, Peter wrote a CAD/CAM program on his computer. Using that program, plus the latest laser- duplicating technology, they supplied me with the mono-block shown in the accompanying photos.

The dimensions of this mono-block are so close to the original that in only two hours, working with candle, file, and stones, I had it fitted to the circle and on-face as shown in the two photos. I am showing you what CAN be done with modern technology and the right friends. I imagine that the cost to have this kind of job done would probably be cost-prohibitive otherwise, but it CAN be done.

Because the .410 action is so small, and the tolerances so close, I don’t feel comfortable to thread the barrels and the mono-block, as I have always done in the past. I therefore decided to shrink-fit the barrels into the mono-block by shrinking them with liquid nitrogen first. I turned the shanks of the barrels down to within .006” of the .625” bores in the mono-block. I then took them to a local precision-grinding shop and they finished the shanks for me to .626”. The cost to have this done was very reasonable, only $40.The last photo shows a jig that I’ve made up, out of some aluminum bar stock, and two lengths of ¼” threaded rod. I believe that the photo, showing the washers, heavy coil springs, and large nut, is self-explanatory. This will be used to clamp the chilled barrels tightly into the mono-block, as the temperatures normalize. I’m hoping that this will result in a fairly close-fitting seam. More to follow…

Edited by CptCurl (04/05/14 09:12 PM)

Post Extras