I wonder if a few of you RUM and WSM loaders would mind measuring the case head on a few cases.
I'm hearing .546"-ish for both, even though WSM is supposedly a nominal .005" wider.
-And Quality Cartridge is apparently using 404 brass (.541" base) to load "RUM" cartridges!
Thanks.

My, 300RUM. factory base's measure .534", same as the the hornady book .

RUM - 0.532
WSM - 0.535

Thanks, guys.
I was referring to the dia above the extractor groove, rather than rim dia.

wsm rim .534
groove .478
body .550

jeffe

I measure my 7WSM at the about where the F/L die quits. New WW cases are .550" or even a little less. Once fired go up to about .554". Heavy fired cases go about .555". My Redding F/L die takes them down to about .554" again. BM

Thanks guys.
If the WSM really is measuring .550" - .555" then it really might be a worthwhile difference from the Jeffery case, at about .541".
Wish it came just a weeeee longer, though. At 2.38", it would make a screamer of a 7mm for a 3.1" short action. One grain smaller than the STW, with a bullet seated one caliber-length, if you can believe that.