Every so often I read that loads for military brass have to be reduced compared to loads in commercial brass, on the theory that military brass is thicker.
Having a reasonably accurate digital scale, and having a couple thousand mixed .223/5.56 "range-brass" cases in hand, I thought I'd see. So I weighed all 2000 of 'em, sorting them into three groups. All the cases had been deprimed, sized, pin-tumbled and well dried. The four largest lots are:
836 pieces Lake City of varying years, from 1990 to 2011
323 pieces WCC (Military 5.56)
353 pieces R-P commercial
285 pieces Federal commercial
Here's how the lots sorted out.
LC____31_______778_________27_____93.1% within "normal" range
I took five cases weighing within 0.3 grains of each other out of each lot and did the water test. Not surprisingly, the water capacities were 30.0 to 30.2 grains across all four lots, full to the top with a slight concave meniscus. (I used a strong light to compare the meniscus form, to be sure that I hadn't over or underfilled any.) Now, 0.2 grains variance in water capacity, using a near max load of Varget, (26.4 grains for a 62 grain M855), results in about 1000 psi variance in peak pressure as calculated by Quickload.
Then I took two cases weighing 90.0 and 95.9 grains respectively, (both headstamped FC), and found the water capacities. 30.7 and 29.9 respectively. Same exact results when I picked out two WCC cases having the same dry weights. The Quickload calculation now says 4300 psi variance. Weight sorting to get rid of these outliers seems warranted.
Based on this sample, it would appear that, for the .223/5.56 cartridge, Lake City and WCC brass are not heavier, nor do they have less capacity, on average, than R-P or Federal commercial .223 brass. It also seems to me that that variance, (within the WCC and Federal lots especially), is a lot more significant than the difference in the probable average weights of the four lots. (I did not have the patience to log the weight of every case so I could calculate actual averages and standard deviations. There are scales that will talk to a database, but I can't afford one.)
Finally, I had a number of odds and sods - PMC, Speer, TZZ, Winchester, S&B, PSD, FC military, which were few enough that I'm not including them in the main analysis.
PSD - 17 of 25 were over 93 grains!
PMC - 30 of 31 in the middle range, one was 93.0 and only five were below 92.0.
S&B - 15 of 15 within the middle cohort.
Wish I had bigger samples of those two.
YMMV of course.