rbstern
03-20-2008, 06:39 PM
My regular load for 357 magnum is a Lee 358-158SWC tumble lube, run through a .358 sizer and lubed with Lars Red Carnauba, sitting on top of 12.5 grains of WC820. Normally, I use Magtech 5 1/2 primers. Chrono testing shows an average of 1288fps out of a 4" S&W Model 66, and 1720fps out of a 20" Rossi M92 for this load. Primers from this load remain fairly well rounded. Get excellent accuracy and minimal leading.
My testing with this jug of WC820 indicates something close to AA#9 speed.
Last week, I substituted WSPM primers for a batch of 50. Shot them, and each and every primer was flat. All 50 rounds, very uniformly flat.
Reviewing my notes, WSPM primers have done this for similar loads ranging from 12 to 13 grains. I've also used Remington 5 1/2 in similar loads, and like the Magtech, they are resistant to flattening in these loads. I don't have any chrono data for the 12.5 grains with the Rem and Winchester.
Question: Is this a primer power issue, or is the Winchester primer cup softer?
My testing with this jug of WC820 indicates something close to AA#9 speed.
Last week, I substituted WSPM primers for a batch of 50. Shot them, and each and every primer was flat. All 50 rounds, very uniformly flat.
Reviewing my notes, WSPM primers have done this for similar loads ranging from 12 to 13 grains. I've also used Remington 5 1/2 in similar loads, and like the Magtech, they are resistant to flattening in these loads. I don't have any chrono data for the 12.5 grains with the Rem and Winchester.
Question: Is this a primer power issue, or is the Winchester primer cup softer?