Measuring Die Neck Diameter without Pin Gauges?

[ntsqd]

Use cerrosafe to make a casting of the neck area. Use modeling clay to plug the top of the die. Follow the directions for dimensional stability.

Beat me to it. Exactly what I was going to suggest.

Although the limited number of cases that I've expanded using a mandrel has shortly come to be my preferred way to perform that operation. At which point the only reason to know and possibly tune the die's ID is to control how much you're working the brass.

 

[Dean2]

I agree with you about not being able to change the diameter without lapping, but knowing the precise diameter would still let me know what the tension would be for different thicknesses of brass, and the stock RCBS die might coincidentally happen to be a good match "as-is" for one type of brass or another. For example, my 6.5 Creedmoor Remington brass measures .012" neck thickness and my Lapua measures .014". Using Forster's die honing recommendations, if the RCBS die is at their max diameter tolerance (.285"), it's a good fit (loaded round -.003") for using on my Remington brass without an expander ball. If it's right on spec (.283), it's a good fit (loaded round -.005") for using on Remington brass with an expander.

Run brass into die without expander in place, measure neck diameter with your Vernier or better yet Micrometer. Presto, accurate neck size that includes the brass spring back, which is actually the measurement you care about.

Now you can adjust tension via neck turning or changing the size of the expander ball.You can't make the tension more than you start with but you can make it less.

 

[nicholasjohn]

Use cerrosafe to make a casting of the neck area. Use modeling clay to plug the top of the die. Follow the directions for dimensional stability.

I'll second that one. I was going to bring this up, but you beat me to the punch. I would think this would be the cheapest and handiest way to accomplish the task, and the stuff is re-usable. You could melt it down and do the same thing with other dies.

 

[Dragoon300]

Don't mess with your die, do as mentioned above and remove the expander ball. Decide the neck size you need or would like and get a mandrel to size it. This is much better than trying to hold your neck ID than with the expander ball, plus is easier on the brass.

 

[DrSteve]

Don't mess with your die, do as mentioned above and remove the expander ball. Decide the neck size you need or would like and get a mandrel to size it. This is much better than trying to hold your neck ID than with the expander ball, plus is easier on the brass.

Thanks for the good advice.