Question on setting up sizing die for once-fired brass

[Western Living]

I have a few thousand pieces of 223 brass from Speer Gold Dot factory loads that were fired once. I intend to load them for this one rifle, but I do not expect to fire them many times. I want to know where I should set the shoulder.

Background
I deprimed them with a universal decapping die.
I'm setting up a Redding Full Length Type-S Bushing die. I've got the correct SAC bushing in the die so it squeezes the neck down such that the Redding carbide button pulls it out 1 thou. I'm not going to do a mandrel die for this volume.

Base to Shoulder Datum
I put the appropriate case comparator in my calipers, a once-fired Speer case, and zeroed it.
I took at least a dozen cases and fired them several times each to fully expand them to my rifle's chamber.
The fully expanded cases are +2 thou BTS.

What should my goal for the BTS dimension be?
Bear in mind this is a semi-automatic rifle so I cannot use the bolt-close method.
+1 thou should be 1 thou under the chamber dimension.
0 should be 2 thou under the chamber dimension.
General rule-of-thumb is 2 thou under chamber dimension for semi-auto actions.

I think I should resize the cases while keeping the BTS dimension the same as a once fired case.
I believe when I resize the cases, it will raise the shoulder 1 or 2 thou.
With careful adjustment, I think I can have the die push the shoulder back down to +0 compared to a once fired case.

Does this plan make sense? Is there something I fail to understand? Ordinarily, I would fire brass several times and use the bolt-close method to set my die and BTS dimension. In this case, I do not want to fire the brass any more, but want to set up as intelligently as possible before I size thousands.

 

[marchboom]

With a semi-auto I would go for .003" shoulder set-back (for reliable feeding) BUT try it the way you described and see if it works. If it does, go for it. Semi-autos are always a pain to determine accurate base-to-shoulder measurements.

 

[Western Living]

I did some more measuring.

It looks like my maximum chamber dimension is +3 or +4 thou over most of the once fired brass. I found a few pieces of multiple-fired brass that big.
If I resize the once-fired brass, the shoulder is pushed up +1 thou, not more.

It looks like if I size the body without pushing the shoulder, I can get the once fired brass to 2 or 3 thou under the BTS of the biggest pieces of brass I was able to fire form. This shoulder will be a pushed-up shoulder rather than a shoulder that has been bumped down. Should I run with that?

 

[marchboom]

When I resize brass the only thing I check is the base-to-shoulder distance with a Hornady type device. If it's where I want it, I'm good. Then I check to see if I have to trim the neck.

With a semi-auto reliability is the main concern, then accuracy.

 

[simonp]

.003 is the default that I have always been told and read for a semi auto for reliable feeding. Less may work depending on your barrel and purpose, for example I have run zero headspace brass before and it runs fine but that is brass that I have sorted and used for zeroing or just when I was shooting less than 50 rounds and the gun was clean.

If going to a class and shooting hundreds of rounds then .003-.004 is where I size my brass to.

 

[99mpower]

.002 if you want to risk the biscuit… .003 to be safe

auto drive or progressive… BTS setback .003

single stage/turret, .002 setback

let her eat

once you do 5-10 pieces depending on what you set it to.. make sure it chamber’s/ejects, before you start going crazy on 500+ pieces