Home Forums Reloading Big Game Rifles Case Comparison

The Lapua thread got me thinking about different cases and their consistency, so I figured I would measure/weigh some and see what differences I got between the two batches of new brass I had at home. I had a new bag of Winchester 243 Win brass and a new bag of RP .25-06 Rem brass. I weighed the cases to see how close their weights were, then checked all the cases for neck thickness variance. Before any comments, I had time at work and this seemed more enjoyable then reading on the internet.

Winchester brass- weight between 156g-162g. 2% 157g, 6% 158g, 15% 159g, 40% 160g, 26% 161g, 2% 162g. The neck thickness varied by 0.001 inches in 43 of the 47 cases. 4 cases had 0.002 inches of variance.

RP brass- weight between 191-195g. 4% 191g, 37% 192g, 31% 193g, 22% 194g, and 6% 195g. The neck thickness varied more with 15 of the cases having 0.001 inches difference, 26 cases having 0.002 inches of difference, and 10 having 0.003 inches of difference.

Again, a bunch of number that I doubt will make any difference on the target. I have read that greater than 0.003 inches of neck thickness variance is too much, so I guess I dont need to cull any cases. Both cases have the bell shaped curve for weight as well.

Sorry to waste your time, but hopefully someone will find this interesting.

Any thought?

Which set of cases would you consider better? The Winchester with the lesser neck thickness variance or the RP with less weight difference?

Necks that are .003" thicker on one side than the other are junk for accuracy purposes.

I'd sort for necks with less than .0015" variation before I took the time to weigh the first one.

I find it interesting and very similar to what I've experienced in weighing cases.

I've gotten to the point, at least in my mind, that case weight just isn't that critical. I've weight sorted case but I now tend to believe that within 3 grains for a .308 is plenty good enough and even with that it's probably way more detail oriented than need be. It's been proven by many folks that weighing cases and tossing out brass is a waste of time. I've done it just because I can.

I think that .003" variance in neck thickness is too much. I'd be inclined to go with less than .0015". .003" plus a liitle bit more from the seating or sizing process adds up to a lot of runout and that's not a good thing. My goal is to hold total runout on a loaded round to less than .003".

The WW brass seems better to me.

Question for you. Did the variance in neck thickness correlate to weight or were they spread out over the weight ranges? Just curious.

With the RP cases, the variance did not correlate with the weight, the thickness did however. For example, the 191g cases were between 0.012-0.014 inches; the 195g cases were between 0.015-0.016 inches in thickness.

The Winchester brass had one case with 0.002 variance that weighed 158g, two at 160g, and 1 at 161g.

Mathman, thanks for your input. I wrote the thickness of each on the case and plan to try to shoot groups with the 0.003 cases in comparison to the 0.001 cases to see if I can notice a difference in my gun. I did sort them out, so it will be easy to cull those cases if necessary.

Don't get too wrapped up yet. You're working with new cases which, even if they have perfect necks, are not necessarily very straight overall.

To make nitty gritty accuracy comparisons you'll want to work with once fired cases that have been sized as straight as you can get them.

Gotcha, was planning on measuring some once fired brass soon and compare to the new cases.

Do you still cull the 0.003 cases or turn them?

The problem with neck turning cases that .003" out is the body of the cases are still uneven. It's supposed to contribute to the bannana effect and add to runout. That's what I've read anyways.

They're culled.

My best stuff is made with once fired cases that have .001" or less neck wall variation. I can size them straight, and with these I'm able to assemble straight cartridges that have consistent neck tension.

Good case necks and straight cartridges are a big part of the accuracy equation. I find it interesting that many people are willing to take the time to weigh each powder charge to the nth degree, but at the same time have no idea about the uniformity of their brass or how straight their finished cartridges are.

When considering a cartridge the first thing I consider is "Can I get quality brass?". I don't think you can make a silk purse out of a sow's ear, and go for the best brass I can get. In most cases that would be Lapua. Here is a comparison of .223 cases which you can find at the 6BR Site .

[img]http://www.6mmbr.com/223rem.html[/img]

I don't find brass the expensive part of loading, and go with the best I can get from day one.