6mm br

[mgva]

I just purchased a custom Mauser in 6mm br Rem that was built in the 1970s. I understand that the current 6mm br Norma brass is .040 longer in the neck and maybe a bit bigger in the body. Can I take a 6mm br finish reamer and cut the neck .040 deeper?
Thanks
Dennis

[gunnut69]

Only if the reamer you use has the .040 longer neck built into it. A chamber cast of the existing chamber should tell you what you have.. Why would current brass be longer than previously made? The longer brass could also just be cut down to match the current chamber. Do you have brass you've already used in the rifle?  Something just doesn't seem right here..

[curteric]

gunnut69
There is some difference in the 6mm br cases over time. it was standardized in 1989.  You are right to recommend a chamber cast to find out what he has. Not only could the neck length be different, but the neck diameter could be also. Tight necked 6 br's are common. Brass life is really good in this caliber so I would make brass fit rather than re-chamber, and only change the chamber if I needed to re barrel. The brass would still work in the new barrel.

[mgva]

I have never fired this gun.  In the 1970's, the 6mm br rem had a total length of 1.510. When it was standardized the neck length was increased and total length is now 1.550. I have the early chamber. Plus with the case trimmed ans sized, it is still tight.  That's why I would like to change to the current spec.  It seem to me that using the proper finish reamer would be the answer, or can I just neck ream the chamber?
Dennis

[Nobade]

Were it mine, I would first check the headspace with a set of real 6mm BR guages. If it is in spec, then hand turn a 6mm BR Norma reamer (With a snug fitting pilot) with the barreled action held vertically in a padded vise. When you felt the shoulder touch, stop. This will lengthen the neck and cut a new throat without changing the headspace. If the body needs polishing you can use sandpaper on a split dowel run by a drill motor.  This should work, and the weight of the reamer with extension and T handle will be sufficient to drive it forward. Just do not turn the reamer backward or you will scratch the chamber. If you have a bore scope all the better, so you can keep an eye on your progress.

[gunnut69]

Quess I'm just a pessimist but I always check to be sure. You may know how the rifle was built but perhaps not all that's been done to it since then. Never cut with first hand knowledge...check the chamber first. Nobade's procedure is spot on but I usually don't use sand paper unless fairly aggrssive work needed.. Very fine abrasives are OK though. My final polish is usually a bit of fine or extra fine steel wool on a worn out brass brush.. wool mop or nylon bristle brush work also. Just wrap the brush head with the steel wool (00 is great) and run the drill motor slowly to wrap it around in the correct direction. An old cleaning rod without the handle works great or a steel rod with a tapped hole to mount the cleaning tool. Steel must be polished and edges deburred.. The wool burnishes the chamber with almost no metal removal. It even works on those stubborn HandiRifle chamber that want to hang onto cases.. On should stay out of the throat if as much as possible..