Now that idea I like! Thanks! Will it make any difference to case capacity? Would my 7mm dies be O.K. to directly size the 300 case with, or is there some intermediate step that I should take?

Brand new Encore barrel, never been fired, ordered direct from the factory.

A common recommendation for case forming is to take a fast burning powder like Red Dot, Bullseye, etc., see how much it takes to fill the case completely, and load about 20% of that. Fill the rest of the case with something like grits or Cream of Wheat. (Dry.) Leave enough room for a little wad of tissue or something to keep it all in the case till fired. Aim it in a safe direction, as even blanks can do a lot of damage up close. I'd lightly lube the cases so they can slide back in the chamber and expand mainly at the shoulder, rather than binding in the chamber and stretching the brass right ahead of the case web.

The more important question is, why are your cases short in the chamber? Have you compared their measurements with a case drawing for the cartridge to see if they're out of spec? Could your barrel be chambered too deeply? Is this a new barrel? It's not a used one that could've been rechambered to some "improved" cartridge, is it?

Worriedman,

First trim the 300 WM brass back to about 2.5" with a .30 pilot and then chamfer the necks well inside and out.

Then just run the case into a 7mm RM FL die.

Trim again to 2.490" and your ready to load.

Don't worry about case capacity.

If you want to size DOWN, an even better idea is to use 358 Norma Mag brass. It's .040" longer in the body and you can set the shoulder back to EXACTLY what you want. Not likely you'd have to worry about the necks thickening either, it would likely not be over a thou and those sloppy necks can easily handle that. Not trimming, no neck turning, and no donuts in the neck down the road, and you have better brass to start.

I have a T/C Encore in 7mm. New brass (R/P), neck sized only seats below the end of the chamber. The chamber to frame gap is .005. so I figure that I should size the brass to seat .004 out from the end of the chamber. What bullet/powder combination is correct to blow the shoulder forward?

I do appreciated the info. Will get that started this afternoon, if I can locate some brass in Memphis!

Showing my ignorance here, but; forming a"false" shoulder by necking up, I would suppose you mean expand the case neck, then neck size it back to correct diameter for 7mm and leave the .30 dimension at the shoulder to hold the case in place to fire form?? Load a light load or standard, and would it be best to seat the bullet out to the rifling?

Thanks, I do appreciate all the help.

Savage99 nailed it -- just adjust your sizing die so that the bolt will just close on reformed .300 Win Mag cases.

Result is a case headspacing on the shoulder, not the belt, and zero stretch.

.300 Win Mag cases are likely to be cheaper and easier to find than .358 Norma cases (which I think have a shorter body than does the .300 Win Mag for what it is worth).

jpb

The BEST approach would be to form a "false shouler" on the case necks by necking them up to .30 or .338, or start with something like .338 cases, then size them down in increments until you get cases on which the action will just barely close. Then when you fire the forming loads, there will be no stretching other than the action would permit anyway.



It is very true that belted cases are SYUPPOSED to headspace on the belt. However, yours aren't going to, so you have really two choices: either start out using the shoulder for eadspacing, in which case you have to make "custom" fitted brass for your chamber, OR send the barrel back to TC and have them send you one with a properly cut chamber.

That makes sense to me. I thought that was the whole point of the "belt" to head space the cartridge. I shoot the 7mm in a Roger bolt action, and my fired cases from it seat below the end of the barrel on the Encore as well as the new brass. Might need to send this one back to T.C.