Does anyone know how much smaller a sizing die should be relative to the chamber?

For example, if I've made a reamer for a 7 x 57 AI with neck = 0.278, shoulder = 0.455 and base = 0.470, how much smaller at these dimensions should I make the reamer for the sizing die?

TIA!

Brass will spring back some after being sized. As far as the neck and shoulder, somewhere around .003" smaller should get it. Maybe .004". The base should be held basicallt the same as unfired brass. Since the web is solid, for the most part, it only needs to be returned to it's original size. So this dimension should be about the same as the brass. Don't know who you are getting your reamer from, but if you call David Kiff, he can lend some excellent advise.

Thanks very much Wayne. I'll try 0.003 at the neck and shoulder and polish until it works well.

The reamer is my own creation from Clymer specs. It took a few tries to get it right but it cuts pretty well. I've been using standard dies to neck size but they're taking a bit off the shoulder and so its time to make dies too.

All this machining is almost as much fun as shooting.

Thanks again!

I've just been going through this with my 20 tactical.

I made the die .003 smaller, and though it will size them enough to grip the bullets when you are sizing down the 223 brass, it does not size the once fired brass enough for the neck to grip the bullet. .0035 or .004 smaller should be right on. I think .003 for the shoulder and body is OK, I don't seem to have a problem with chambering but getting the tension on the bullets.