[Spitnine]

Originally Posted by mtscott

Hello, my dad picked me up some primers this week. My IMR reloading data calls for Federal Premium Primers (PN - GM215M) and he got me the non-premium ones (PN - 215). These are for a 300 WTB Mag.
Can someone tell me what the difference is between the two and if I can use the non-premium primers for my 300 WBY Mag?
PN - 215: http://www.midwayusa.com/eproductpag...eitemid=586171
PN - GM215M: http://www.midwayusa.com/eproductpag...eitemid=184351
Thanks!!!

I suspect the Federal #GM215M primers are "magnum" primers, similar to Remington's #9 1/2M primers.
Magnum primers, which are a little "hotter" than standard primers are often recommended for magnum calibers with large case capacities.
Some also use them in reloads intended for use in very cold weather.
I've used both (Rem) in .308 Winchester and never noticed any difference.
There is some buzz out there about possible pressure problems with magnum primers in non-magnum cases. Don't know if it's accurate or not.
I would say that you are safe to use magnum primers in your 300 Mag.
Thanks.