Sizing WW 6mm Remington brass to form wildcat 22/6mm. Case necks are too thick resulting in tight chambering and poor groups.

Trying case neck reaming.

Technique...

Size factory new cases to 22/6mm. Neck ream with Forster neck reaming tool. Trim cases. Size again to 22/6mm. Don't feel cases slide over neck expander. Bullets fit so loose that they slide under own weight. Leave bullet seated long and let closing rifle bolt seat bullets. Now get good groups.

Obviously, can't use this method for field use.

Yes, can use neck turning tool to adjust neck thickness but very slow for forming so many cases.

Please recommend speedy technique for reducing case neck thickness.

Hammer

I think before this situation can be adequately handled you are going to have to collect some information. Inside and outside diameter readings before and after sizing and both after reaming.The neck outside diameter coming out of the die without the expander before you ream. Can you slug your chamber or whatever(drill rod?) and get an accurate chamber neck diameter? If you can do this than you can get the right size reamer and be off and running. roger

What is the wall thickness of the 6mm Rem brass now? Compare it to the wall thickness of a WW 257 Roberts case and see if they are less. Can you push a bullet into a fired case neck before it's sized?

If this does not work I suggest having the chamber neck reamed or polished out.

Another idea is to neck turn the existing brass. Varmint Al's site has a decent description on how to neck turn.

You've obviously shot some so that you have some fired cases. Measuring the diameter of the neck of the fired cases will give you a chamber measurement for your neck that's quite close. Measure that and you have one measurement. Also, whomever chambered your rifle can measure the reamer and tell you. From there it's a simple matter of arithmetic.

Measure an unreamed case with a seated bullet and figure what you have to take off the walls to get you at least .002" clearance on your seated bullets. Reaming with the Forster tool isn't the best course. The reamer follows the path of least resistance and will give you some uneven neck walls. That will stovepipe the neck and not help accuracy. Precise neck turning is about the only way unless you want to spring for a reamer die and reamer that Redding can make for you. There is no "fast" or "easy" way. Welcome the the expensive world of wildcatting!