While resizing/depriming a mixed batch of .223 cases, I noticed that several of the cases resized and deprimed significantly harder than others. At first I thought that it might be that some cases weren't adequately sprayed with lube, but then I realized that virtually all of the cases giving me difficulty were Prvi Partisan (PPU) match cases. I began keeping track of them, and noticed quite a variation in the ease of resizing the PPU cases, that wasn't there in other brands of cases. Here is what I observed:
Prvi Partisan: Mostly an order of magnitude stiffer in resizing and decapping, with a few extremely difficult, and some quite easy.
PMC Bronze: Sweethearts to resize and deprime. Very consistent.
Remington: Also very easy to resize and deprime. Very consistent.
Federal American Eagle: Easy to resize and deprime, despite having crimped primers.
WCC '09 5.56mm. Easy to resize and deprime, despite crimped primers.
Seller & Belloit: Fairly easy to work, but with a few that were more difficult.
There was so much variation in the PPUs, that I saved out one of the more difficult, one of average toughness, and one of the easy ones. I then decided to weigh, measure, and check capacity of each of these cases, plus three randomly selected cases from each of the other headstamps. Here are the results:
The case weights are in grains, and the powder capacity was measured by priming the cases, filling them to overflowing with Varget, leveling the top of the case with a steel ruler, and dumping the powder onto the scale pan.
Not surprisingly, the most difficult PPU case weighed the most, at 96 grains, while the easiest one weighed least, at 93.9 grains. They were the most inconsistent with an average variance of 0.80 grains. I had rather naively thought that, being match ammo, their cases would be most consistent.
The most consistent were the WCC military cases with only 0.00667 grains average variance, followed by the PMC cases, at 0.02 grains.
Of course, three cases isn't an adequate sample to draw too many conclusions with, but as I recall, the WWCs and PMCs were very uniform in how they went through the resizing/depriming operation.
It would seem that the strongest cases would be the Seller and Belloit, but at the expense of case capacity.
Also, it's pretty comforting to know that you apparently can't stuff enough Varget into a .223 case to get into too much trouble, as the maximum loads for most 55-60 gr. bullets are around 27 grains. Double-charging a case is definitely not an issue.
I had been loading mostly PPU cases simply because I had a lot of them. For accuracy, though, I'm going to look at going with WCC military and PMC cases.
Thought this might be of interest.