The reason for rehardening would, perhaps, be to maintain good wear charactaristics. As well, soft material has a tendency to be "sticky". Regards, Bill.

So, if I did stone the rails of my stainless MRC, how would I reharden it? Does 416R stainless even need hardening? Can it even be done?

Old Mausers are carbon steel, case hardened, usually in a bone charcoal pack. Sort of a lost art. Later Mausers like the MarkX are not case hardened, most folks say they are made from heat treated 4140.

Modern receivers (4140 or 416 SS or another SS alloy) are heat treated to increase the yield strength of the material, but not case hardened.

So, aggressive polishing of Mauser raceways will get you below the case and you will no longer have that nice smooth "semi glass hard" feel when the bolt is cycled. If you polish this aggressively, you will enlarge the dimensions and have a sloppy bolt fit.

Same thing with lapping or recutting the lugs on a Mauser: You may get under the case, thus you will have soft lug faces prone to gauling. Generally the case is hard, so it takes a lot of elbow grease to get below it when lapping.

Since modern receivers have no thin case, polishing will not remove it. Just do not take out too much, otherwise you will have a sloppy bolt fit.

You don't need the reharden the MRC. Stoning removes only the high, rough spots and doesn't truly get below the surface if it's done correctly.



What would it matter if you "got below the surface" with an MRC 1999, anyway? The MRCs are not case hardened, but through hardened, right? So isn't the factory surface insignificantly different from the metal deeper down and all the way to the core?

You don't need the reharden the MRC. Stoning removes only the high, rough spots and doesn't truly get below the surface if it's done correctly. I believe what Bill Leeper was referring to was the Mausers that are very worn. Polishing stones only take the microscopic peaks off the surface of the metal in the raceways and some areas are left untouched. I used the frangible polishing stones epoxied to piece of aluminum flat stock. Not many passes and it's done. You probably don't remove more than a thousandth or two in most areas. The stones wear enough to conform to the dovetailed raceway and take care of any problems there. The biggest problem I had was stoning the bridge where mine was very tight. I also ended up jewelling the bolt to help it slide effortlessly through that area. Works as slick as any chromoly now. You can get the stones from MRC or a similar tooling supplier.

Hey Bob338,
That sounds like a good technique. I'll try it on a rough Ruger (aren't they all?) in (drum roll please...) 338.

Hey Infosponge,
I hear your momma calling you back to the political forum. BTW, I told you to use an old manual typewriter to make those fake memos you did for Mr. Dan over at CBS. Can't you get anything right?
I heard he was pretty mad at you. He was walking down the hallway at the news studios yelling "where is that goddamn Forrest Gump Sponge?" "I'm gonna wring his geek ass pencil neck when I get a hold of him!"

JCN

I have no intention to discuss the metallurgy of MRC actions on the politics forum, nor to discuss politics with you on this forum, John.