Size of custom resizing die?

[Trailblazer]

I want to try making a resizing die on a lathe. Most of my sizing dies are small and overwork the brass. It doesn't matter on the calibers I don't shoot often but it does matter on the ones I shoot a lot. I have a RCBS 30-30 die set that they must have screwed up on. The neck comes out just about perfect. The expander ball lightly drags through the neck on most cases and it doesn't even touch on thin necked cases. I would like to have more dies like that one! It isn't only the neck that is the problem. I can't get away with just neck sizing on a couple of my rifles, probably because of things not being concentric. The cases need to be trimmed more often when I full length size, which I think is because the brass you mash out of the shoulder ends up in the neck.

I am going to make a chamber cast and then want to cut the die to fit the chamber. The question is how much smaller the die should be to size the brass enough. I have read that wildcat chamber reamer sets have a roughing reamer .002" smaller than the finish reamer so that you can cut a die with the rougher. .002" doesn't seem like much. Especially with harder springier cases. OTOH if the cases are only used in one chamber maybe it is enough. The neck would have to be sized more than .002" undersize for sure. What say you?

[StarMetal]

Just buy a neck sizing only die.

Joe

[Doughty]

Trailblazer

There is an interesting article on this subject in the Single Shot Rifle Journal, Vol. 59, No.3, which is the May-June 2005 issue. The article is [I]A Long-range Rifle: Part 3., written by Steve Durren. I think you can find them on the Web at assra.com if you want to get a copy. If you're inclined towards these sort of projects you might want to subscribe.

If I read him right, he is cutting .001 smaller than finish size, to allow for polishing, but doesn't state just how much smaller finish die size is than chamber size. And if I understand you, this is exactly what you want to know.

If nobody on this board comes up with an answer, you might get one from him. Dang it all, now you've got me curious. If you find out let us know.

[HotGuns]

Having made several resizing dies on a lathe I've used .003 as a happy medium with no problems thus far. The last die I made was for a .50 BMG and the .003 neck size seems to work well with plenty of tension.

I dont think that there is an actual "standard" for tension sizes on necks but I could be wrong. I've measured everything from .002 -.005 on various calibers and even same calibers with different brands will show a difference.

I would think that the ideal measurerment would be one that works the brass as little as possible yet still be able to take the pounding of rifle fire without the bullet setting back as it lays in the magazine. You must also have enough tension to jack the cartridge out of the chamber without pulling the bullet out.

On a single shot rifle, neck tension is less critical.

I guess that thats one of the reasons for using custom dies.

[Trailblazer]

Hotguns, did you make the die body .003" smaller than the chamber? And how did you polish the die? I thought I might make a lead cast and lap it. Maybe there is a better way?

Old Vic, I will take a look at the ASSRA site. Although I certainly don't need any more ideas for new projects!

I could make a cerrosafe casting in a die also and see how a sized case compares to the die casting. .003" doesn't sound like a bad number to start with though.

[HotGuns]

Trailblazer...

I only neck size.

I use Lee Collet Dies for a pattern. The neck size collet dies use an insert that sizes only the neck. The beauty of that arrangement is that you can change out the inserts to experiment with different tensions. For instance, if you make one with a size difference of .002 and you decide that you dont like it, rather than make the whole die over again, you simply make another insert with different dimensions and try again. Since the insert is only a piece of steel with the same O.D. and a different I.D., it's much quicker to make.

If you keep your tolerances pretty tight, you'll have virtually no runout to have to contend with.

For a start on polishing, I'll use a high speed with a fine feed. Then I'll take a small dowel rod and slit it and put various grades of emery cloth around it and insert while moving back and forth. For the final finish, polishing compound works well and will give almost a mirror finish.