Hmm,
A small rifle primer is adequate for .223, .222 using 20-27gr of powder, but a .30 Carb with 12-15 needs a magnum? I think not.
The military used a standard primer from 1942 till production stopped in the '60's, and powder was always a spherical powder. It can be argued that the original Olin produced primer was a magnum level primer, but then Speer uses a CCI primer. I suspect they probably know what's in that primer.
I've used Winchester, CCI, Federal, Tula, Remington, Selier & Bellot, and Privi Partisan small rifle as well as CCI, Federal, and Winchester small rifle MAGNUM primers and neither I nor my chronograph can detect a significant difference. However, it seldom gets below 0degF in Georgia.
Neither my Speer #9, Hodgdon #24, Lee #2, Hornady #5, Hornady #8, Lyman #48, nor Sierra 1978, or 1984 specify a small rifle magnum primer.
If I was going to re-enact the battle for the Frozen Chosin, I'd be sure to use magnum primers.
I suppose primers aren't as strong, and powders harder to ignite than they used to be.
FWIW, I use a small pistol primer in my .22Hornet and .218Bee to get improved accuracy, and use Hod Lil'Gun and H110- spherical powders.
I use small rifle in the .30 Carbine as I also use same loads in the rifle to avoid cratered primers or slam-fires.