Chronoed some loads today for my 30-06; 62.0 grains of Ramshot Hunter with 165 gr Hornady GMX bullets and CCI 200 and Fed 215 primers. The loads with the magnum primers were 40 fps slower than the large rifle primers. Anyone else notice this before?

Primer compounds are not all the same and don’t function the same way. It doesn’t surprise me that your test produced a difference of +- 40 fps. Just because a primer is called magnum doesn’t mean that it should increase the velocity of your load. The primer should start the explosion but not be a part of the explosion. My question to you is; which one had the most consistent group on the target?

The magnum primers gave the lower Extreme Spread but the group sizes were nearly the same. The group size could be my fault. I also shoot IMR 4350 with the same bullets. They grouped better but the ES was a lot larger.

Chris,

I ran experiments with primers in a number of different cartridges with a number of primer brands and of course LR and MLR. Most of the testing I did was years ago and since then I have lost that information (sloppy and careless record keeping in my youth).

What I found was the same as you and like you I was surprised that a MLR primer didn’t produce more velocity, I don’t recall a magnum primer producing less velocity than a regular primer but I’m not surprised about your test results. I found that magnum primers opened up my groups in the non-magnum rifles I tested (25-06, 270, and 308). In fact, as I remember the 308 turned into a shotgun and did see an increase in velocity. On the other hand my magnum cartridges (7mm Remington Mag and 300 Winchester Mag) really liked magnum primers but they also liked LR primers too, WLR worked very well.

If I were to run these tests today, it’s possible that I would get different results.

Keep playing around with it Chris and form your own opinion, experimentation is one of the reasons we reload.

This is a good thread. I'm interested in velocity/pressure differences between standard and magnum primers. I'd be interested in seeing a Federal 210 vs. 215 comparison test.
The reason I'm interested is, when I was developing loads for my 7mm Magnum years ago, I only had Federal 210M primers on hand. The accuracy I got using them was so good, I decided to continue using them. I wasn't interested in re-testing loads with 215's, just because they have the word Magnum written on the primer box.
The 210's have performed flawlessly in cold weather too, up in Michigan's UP during late November when Deer season is on.

Don

I've been telling fellow reloaders for over 40 years that the only consistent difference between "standard" and "magnum" primers is the price.

quote:

The loads with the magnum primers were 40 fps slower than the large rifle primers.

Aw man...you just had to go try that didn't you! Now you've done it, proven that the oft quoted "comventional wisdom" (?) of "hot" primers being the "best" for everything isn't true!

So, now what's a guy to believe and how can any of us be "gunstore experts" on how to reload?

I often run tests after working up a good load using one primer. Then I will swap match & mag primers & primers of diff. manuf. Sometimes accuracy improves, sometimes vel. goes up or down, it just depends. I do always use a mag primer for powder charges over 65gr or so, well almost always.