SOLVING THE PRIMER SHORTAGE
In the late 1950s, Roy Weatherby and some associates began to experiment with what we still know today as his largest basic rifle cartridge case, the 378 Weatherby Magnum. Since that time, the case has been necked up and down to create a total of five factory cartridges: 30-378 Wby Mag, 338-378 Wby Mag, the original 378 Wby Mag, the 416 Wby Mag, and 460 Wby Mag.
The 378 case is similar in size to the 416 Rigby, but a belt has been added and the case capacity increased by forming less taper in the body. Any way you look at it, this is major-league capacity for a shoulder-fired rifle. Enough so that the large rifle primers of the day were not "hot" enough to reliable engulf all of that powder in their blast. Part of "hot" includes duration of burn, and primers are already tough enough to make correctly.
Federal, one of several primer manufacturers, came to the rescue with their No. 215. This primer had the power to light off the powder in the big case, and power to spare for smaller Wearherby rounds such as the 300 Weatherby Magnum. Therefore, it came to be known as the ultimate magnum rifle primer, and it was exactly what reloaders wanted. Meanwhile,other factory ammunition producers besides Norma (the Weatherby ammo producer) sometimes offered loaded ammunition in cartridges such as the 300 Weatherby Magnum.
How can this be, I wondered? Weatherby uses the Federal 215 Primer in their 300, and in shorter cartridges like the 257 Wby Mag, so is Remington doing that too? Well, no; they were using their own 9-1/2M. So I tried 180-grain 300 magnum rounds from both manufacturers to see just how doggy the Remington loads would be. Hummm... no difference.
This led to a fairly in-depth comparison of hand loads, using only different primers in the 300 Weatherby Magnum. Again, no difference. Why?
The answer that took about two years to confirm was that both Remington and Winchester had re-engineered their large rifle magnum primers to easily handle the Remington Ultra Magnum cartridges, even if they were loaded with difficult-to-ignite ball powders, or other powders with considerable deterrent coating. Now, apparently a lot of top long-range competitors have discovered this as well, or maybe they knew it early on. The evidence is clear to anyone who pores over the details of the loads used by the top shooters at the various matches.
It used to be that most everyone in the midwest just had to have the hard-to-find Federal 215 or Federal 215 M Primers (the M means Match in this instance, the number 215 already indicates magnum), or their world was closing in on them. Not anymore. The erroneous magazine and internet comments have faded into the background, as so many shooters have discovered that the Winchester WLRM and Remington 9-1/2M can now be part of their bag of tricks when it comes to refined accuracy in large-capacity magnum rifle cartridges..
JDC