A 17Mach2 relined barrel that will fit a 142 or a 340 bolt action??? At this point I haven't relined it. It is originally from a model 51M(b). The barrels length currently is 19.625" and all of the original markings are on the barrel. When I remachined the breach end I duplicated the dimensions of the 142/340 barrels as they are the same with only two extra cuts on the 340 versus the 142. Aside from those two cuts the breach ends measure out to be the same for both of these models. I welded up the sight holes then turned the barrel down on a lathe, then filed and polished it so the barrel is "in the white". The stock diameter of the 51M(b) is slightly larger than a stock 142 or 340 barrel so the barrel channel would have to be enlarged to accomodate this barrel in either a 142 or a 340 stock. God Bless, Frank.