Coned breech on a Martini International?

[bguinn]

Has anyone machined a coned breech for a Martini International?

I believe that a coned breech will be self aligning and avoid the complex maching involved in milling the angles for the factory method. I have seen the effect of a misaligned barrel causing the extractor to peen the chamber over time. A coned breech should naturally prevent this.

I see no reason why it would not work, in fact may be better than a coned breech on a bolt gun since the breech block aligns the round very well, and and you'll have no issues with the bolt's forward momentum to deal with.


Any real world experince would be appreciated.

 

[TheoW]

I take it that you're referring to to a BSA .22 Martini Int'l Match. This is a beautiful old designed action which begs the question...why a coned breech? Have I missed something over the decades?

Ted

 

[bguinn]

Ted, if you rebarrel a Martini in the same way the factory set them up you must do several milling operations, unlike a typical 22lr bolt action (requiring 2). If memory serves the number is 9 including the relief for the firing pin. Four of the cuts are at 45 degress in close quarters requiring the right size cutter, or on a cnc (which is how I do it)

I have seen 3 Martinis that due to slight misalignment of barrel tenon/extractor, caused the extractor to bump into the side of the chamber, peening it to the point that each loded round was gashed when chambered - destroying acuracy. On another this caused the extractor to break. As you may know extractor breakage is a bit of a problem with these guns. Cost for a new extractor is ~ $100.

I can cut a coned breech in the same lathe setup used for chambering, literally in a couple of minutes versus the setup in a indexer on a mill which must be aligned precisely or you will have issues with the sensitive extractor alignment. I know one gunsmith that has had a special carbide cutter made to speed up his rebarrelling jobs.

A coned breech cut while chambering will be concentric, and only one setup is required.
A coned breech will also allow you to index the barrel effortlessly, ito any position f desired. The factory setup could at most allow for 2 positions, 180 degrees apart (and this would require 2 additional cuts)