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Redding body die, measuring bump

I have a Redding body die,260 Rem) that i'm trying to understand how to properly measure shoulder bump. I can set the height to engage the shoulder or not but since the case seems to grow as I size the body, how do you measure a .002 bump?

I noticed that if the die contacts the shell holder, my neck is more out of round at this much travel after the sizing. I have less than .001 runout from a fired case, that goes to .0015-.0018 after the body die. I have been using the Lee neck die up to now but wanted to start bumping the shoulder back a bit since some are getting hard to chamber...about 5 firings.

The Lee die will give less than .001 runout and I feel I will need this die if I use the Redding die since it's playing with the neck concentricity.

The inside of the body is clean...no marks or debris.
 
Go here and scroll down the the headspace guage. http://hornadyle.com/story.php?s=485

This tool allows for the measuring adjustments that you are seeking.
 
Here's the Hornady tool:

21dg6yw.jpg


As a cheap, fast work-around, take a fired, sized .45 acp case,with primer removed). Place this over the nose of your .260 case. Measure, with calipers, before and after bumping. It takes a little practice to keep the two cases parallel, but you'll find you can see the difference between no bump, .001" bump,.002" bump.

headspacex300a.jpg



headspacex300b.jpg
 
I've been a long time lurker on this forum, and I've found there's a lot of good shooters here. I just wanted to show you our new Digital Headspace Gauge. It's the easiest way to measure headspace, and it works on ANY caliber. It doesn't require special tools or bushings to operate.

headspaceLB300.jpg
 
The measurement of bump should be relative to a case that has been fired, neck sized only, several times with warm loads. The Hornady tool is what I use for all of my calibers except my 6PPC, which I have a barrel stub for.,squared off short piece of barrel with the front part of the chamber reamed in one end)It is the best tool that I have found for this task. Sinclair makes an almost identical product. As a body or FL die is adjusted down toward the shell holder, the headspace will increase until the die is far enough down for the shoulder part of the die to start bumping the case shoulder at the top of the ram stroke. From that point on, headspace will decrease as the die is adjusted down. Just remember that the coarse die thread means that extremely small amounts of die rotation are required to keep from overshooting the mark.
 
Wanted to add, the Redding body die is sizing my 260 case down .006 at the top of body before shoulder, .003 at mid point and .002 above the base. From an accuracy standpoint is this excessive or normal, and would a custom die giving me max sizing of .002 at top of case be beneficial to accuracy or just case life?
 

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