I made this gage to check the C/L datum of the shoulder of 7 Rem Mag brass.
I have one for all of the cartridges I load for. I also have a control piece for each of my rifles.

The tool and calipers, new brass and my control piece of brass for my rifle.


The gauge


I have zeroed my calipers on the control piece


The new brass is .0205 shorter than my control



As a machinist/moldmaker I have been measuring over a pin gage or a dowel then doing the trig every day for nearly 25 years. Checking brass in this fashion to me is second nature and easy…..I know it is not required it’s just my way.

I just thought I would share.

nice idea. roger

Doesn't a belted magnum headspace off the belt?

It headspaces off the belt, yes....however you don't want to push the shoulder back too far or you work/stretch the brass that much more each time it is fired and quickly have premature head separation of the brass.

I headspace all cases from the shoulder.
I ignore the belt on all belted cartridges.

quote:

I headspace all cases from the shoulder.
I ignore the belt on all belted cartridges.

May I ask what you use for a headspace gage in this case?

I base my control dimension on.....a once fired case from the rifle I am loading for.

Hey ted

Good tool. It is giving you the most important measurement. It would not do you much good in case prep to know what your headspace is on a belted case. We all know that once the case is fired and expanded, then you need to resize to minimize shoulder setback and still chamber freely. Your tool will do that just like the Hornady tool does.

I have measured headspace on many belted cases in different guns and had headspace that measured from 0.000" to 0.007" and those same cases had a gap at the shoulders that measured from .017" to .030". The headspace measurement is inconsequential when you can switch to headspace on the shoulder after fireforming.

I've been making "Wigets" for my handloading customers for years. I use a piece of their barrel and the chamber reamer. I don't make them as long as Ted's. I face them off .025" longer than the chamber, so you can see if the case is getting too long. I also encourage the customer to de-prime the case first, so as to not get a false reading from the spent primer.

Set barrel headspace with proper gauge, setup dies to NOT FLR, therefore your shoulder is now the effective datum, ignoring the belt ... just like neck sizing ignores the "gauge" headspace, and delivers the actual