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| Boltface,
I am no Mauser expert but I can offer some information about reboring.
The barrel to be rebored must be heavy enough so that sufficient wall thickness will remain after it is rebored to the desired caliber. Any features that reduce wall thickness (dovetail cuts, sight mounting holes, flutes, etc.) must also be considered. The bore diameter (the circle that is formed by the tops of the lands) of the new caliber must be at least .005†(and .010†is better) larger than the groove diameter of the old bore. Any less than this and it is almost impossible to achieve a good surface finish when pulling the finish reamer. This means a 25 caliber cannot be rebored to a 6.5mm, a 270 won’t make a 7mm, etc.
The single point cut-rifling method is typically used for reboring. The button rifling method is not suitable for barrels that have already been contoured. New barrels are manufactured by several methods including buttoned, cut, broached, and cold hammer forged. The barrel makers will select steel that gives the best results for their method of manufacture. If something goes wrong while making a new barrel, that work piece is scrapped and a new one takes its place. A reboring shop does not have that luxury and will be asked to rebore barrels that may be one of a kind and could have been hammer forged yesterday, button rifled 30 years ago, cut rifled 130 years ago or anything in between. Further complicating the picture, manufactures can and have changed methods and/or sources over the years. Mausers were built all over the world for several decades including military and commercial versions. It’s likely that you might encounter some variation in the composition and hardness of the barrels used on Mausers (or any other rifle)! This is what makes reboring so interesting! In my experience, Mauser barrels present no special challenges and we are willing to rebore them.
As you can imagine, reboring is not a production line process. Very seldom are two jobs exactly alike. Barrels with different shapes and sizes require a variety of fixturing and oiling methods. The cut rifling process is time consuming but offers the flexibility needed for reboring. The reboring option is not for everyone. Can you get a caliber conversion done for less money? Sure you can. If your needs are well satisfied with a factory take-off barrel or one of the inexpensive mass produced barrels available thru mail order and/or you do your own work or know a hobbyist gunsmith who undercharges for his work you can get your gun shooting for less money. However, if you buy a cut rifled, hand lapped barrel blank and pay a fair price to a professional (that means someone who has to make enough money to pay the light bill, buy tooling, pay the help and have enough left over to pay himself) to install it I think you will find reboring worth a look. Move the discussion to guns with expensive features like engraving, quarter ribs, sights, custom contours (half octagon), expensive finishes, or rifles which require barrels with complicated breech features like Savage 99’s or Winchester ‘95’s and reboring begins to look quite attractive. Fine double rifles are another example. Again, it’s not for everyone but one must have all the facts to make an informed decision. I’m sorry if this has been a little long winded but I have been accused of that before! Feel free to e-mail or PM me with questions. |