Lr or lrm primer for 300wsm?

I have one load for 300WBY 180 TSX and IMR7828 with CCI200 and one load 300WBY 180 Nosler BT, IMR4350 and Remington 9 1/2 Large Rifle (Non magnum). I have never hunted at your temperatures though.

Yeah usually it isn't too cold, but on a rare hunt morning blind hunting can be -20 - -30s.
 
One million large rifle primers just arrived in Alberta....1800 mile (2550 km) round trip 34 hours!
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I use LRs (Fed 210M) in both 300 WM and 300 WSM. They performed the best in my primer test during load development
I have gotten better SD's in certain barrels and loads with non magnum primers (usually 210m's) in 300 wm, 28 nos, 300 prc, 30 nos and 300 wsm. Never had a hang fire or any ignition problems whatsoever in thousands of rounds fired. Cut ES in half going to a non mag in a couple loads.

Seen velocity gains (minimal) in avg velocity over ten shot strings with non mag vs mag with the exact same load. I think it's more powder type than case capacity. H1000 seems to like being sparked with a standard primer, retumbo seems to prefer a magnum. YMMV.
 
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