Shrinking Brass?

[reloader-51]

Hi all,
New to the 204 Forums and wanted to pick the intelligent minds of those reloaders on here. I've been shooting and reloading about 45 years and ran across something yesterday I hadn't seen before. I just purchased a new Savage in 204 and bought the necessary supplies for that round to start reloading. I purchased new Hornady brass, resized it in Redding Type S bushing dies and used a bushing that dropped it down the recommended .001" for bullet tightness. Loaded up about 6 different loads, took them to the range, and fired away. Everything worked fine. Picked out my two best loads and was going to tweek them some, so I tumbled my brass as I always do and cleaned everything up good and started reloading again. As I seated my bullets, I noticed they weren't tight. I checked my dies and everything several times and was stumped for awhile. I decided to do some measuring on the necks. I had a few that had not been tumbled and compared them to the ones that had been tumbled and lost between .002" to .003" on the ones that had been tumbled. I'm talking about the wall thickness of the brass. I have tumbled tons of old and new brass for years with the same type media and used the Redding dies. It looks like now, I'm going to have to drop down a few more thousandths on my bushing for it to size properly. Anyone ever heard of losing that much thickness in brass just from normal tumbling and cleaning?

[Bill K]

Interesting, I have never had any such problem after tumbling brass. Will be interested in hearing what caused the change.. Bill K

[Wrangler John]

Unless you were using some industrial tumbling media, I doubt that commercial cartridge brass media would be the cause of shrinking necks. Most likely the necks were manufactured with the variance. Hornady brass (and others too) has been known to be consistent over all, but with an occasional lot that causes problems, usually split necks, folds in the necks and shoulders. The cause would be more definitive had you measured each piece of brass before loading.

I suspect that the problem is where an abnormally thin piece of brass is sized in a bushing that is too large to produce the desired O.D.. While most of the brass is sized to produce the .001” pull, a few don’t.

Remember that most commercial loading dies rely on over-sizing and then expand the neck I.D. to obtain the desired bullet pull. This allows each piece of brass to work in an imperfect world regardless of the variance. Spring back of the brass must also be accounted for, so that a slightly smaller bushing is necessary to obtain the final dimension.

I checked a few of my fired Winchester cases, the necks measured a uniform .232” O.D.. Sizing them in an Redding neck sizing die with an expander ball resulted in an O.D. of .225”. Neck thickness measured a consistent .011” (+/- .0005”) so that the I.D. of the necks is .203” (.225” O.D. - .022” neck thickness) this establishes a .001” bullet pull.

After removing the expander ball, the case neck O.D. was sized to .222”. The expander ball measured .203” which resulted in a case I.D. of .203” and a neck O.D. of .225” (.203” + .022” neck thickness) establishing a .001” bullet pull.

Conversely, if we have a neck thickness of .010” and size the O.D. to .225” in a bushing die without an expander, the I.D. will be .205” (.225” - .020” = .205” or .001” larger than the bullet O.D.). Using a standard neck sizing die with an expander would result in sizing the neck to an O.D. of .222” with an I.D. of .202”. The expander would open this up to .203” still allowing for a .001” bullet pull.

I would recommend switching to Winchester brass to reduce cost of culling rejects, and size to a small enough O.D. so that the addition of a carbide expander will establish a uniform bullet pull. The only other alternative is to turn case necks – and that opens a whole can of worms. Your Savage should shoot in the .5” range using a neck bushing and expander ball. My .204 is just phenomenally (spooky) accurate with a standard neck sizing die.