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The Ultimate Reloading Manual
Wolfe Publishing Group
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The Ultimate Reloading Manual
load development

Mixed Cases

Author: John Haviland / Wolfe Publishing Co.
Date: Jun 08 2009

Loading powder that fills the case when the bullet is seated helps reduce velocity swings.

Fastidious handloaders sim­ply know their reloads will provide the most uniform velocities and the best accuracy when they use the same brand of cases. Cases of different makes can vary in internal volume up to several grains of powder, which can lead to swings in velocity. But by using all one brand of cases, and even cases from the same lot, velocity will be more constant and accuracy the best possible.

After running an experiment with two common cartridges shoot­ing the same make of cases from the same lot and a mix of case brands with a couple of different powders, I can definitely answer seeking perfec­tion via using the same cases may or may not be worth the bother.

The first rifle I tested was a Sav­age Predator Hunter .223 Reming­ton. Barnes 40-grain Varminator bullets were used with H-4198 and W-748 powders in the same lot of Winchester cases and a mix of com­mercial and military cases. Each charge of powder was weighed on a scale, cases trimmed to the same length, the same primers used and all bullets seated to the same depth.

With the .223 accuracy was good with
W-748 and Barnes 40-grain bullets.
The .223 mixed case group with W-748
had a definite vertical string to it.

Military cases usually have thicker walls than commercial cases, which can reduce powder capacity somewhat and produce higher pres­sures. So when using military cases, it’s a good idea to back off maxi­mum powder charges a grain or two. The two powders used in the .223 loads were about one grain below maximum and in the military cases showed no signs of excessive pres­sure. The military cases used were Lake City ’83, ’85, ’94 and ’97 for some of the .223 Remington loads listed in the table. Those cases pro­duced most of the faster velocities, showing they had somewhat smaller internal capacities than commercial cases.

The second rifle was a Ruger MKII .30-06. The Ruger is a basic hunting rifle that on an average day groups five shots in about 1.5 inches and on a good day three shots in maybe an inch. For its loads, Berger 168-grain Match bullets were used with W-760 and IMR-4350. The Berger bullets and each powder were loaded in Hornady cases from the same box and Federal, Remington, Hornady, RWS and Winchester cases. Everything else was kept the same.

Follow along with the shooting results listed in the table.

Velocity

With the Ruger .30-06 shooting Berger 168-grain bullets over 52.0 grains of W-760, there was a slightly less extreme spread of velocity with Hornady cases compared to the mixed brands of cases. The relatively high extreme spread of velocity with the Hornady and mixed cases was probably because the 52.0 grains of W-760 did not quite fill any of the cases with the bullets seated. That allowed the powder to settle any which way in the cases and on firing produce a relatively wide extreme spread of velocities.

The .223 group with H-4198 and all Winchester
cases grouped four bullets tightly, but alas, one
bullet landed wide.

Extreme spread of velocity is reduced substantially, though, when cases are filled with enough powder that

The .223 group with H-4198 and mixed case brands
had a nice round shape but wasn’t as tight as
the group with all Winchester cases.

seating bullets slightly com­presses the powder charge. That is if all the cases are the same make. Seat­ing Berger bullets in Hornady cases slightly compressed 58.0 grains of IMR-4350. With the powder charge locked in one position in cases with the same capacity, extreme spread over five shots dropped down to a decent 19 fps. The same amount of IMR-4350 seemed to be compressed when bullets were seated in the five different brands of .30-06 cases. But the varying case capacities of the five brands still produced three times the velocity spread as cases of all the same brand and capacity.



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