The thread of DB Bill has shown that for the 7mm Remington and with a given load the variance of velocitiy is insignificant but the variance of pressure is quite important when we change the brand of primer. In this particular case my assumption proved to be more or less correct that hotter primer tend to produce higher pressure. If this were a general rule this would mean that generally the best results are achieved with a mild primer.

Due to my reloading experience with a very limited number of cartridges only (7,5x55 swiss, 7x64, 222, where the above tendency semms to exist, I ask you colleages whether you have made similar observations or whether particular types, capacities and forms of the case confirm or contradict this rule.

The very last thing I've always done in developing a load is to switch to a variety of primers. About 30% of the time I've noted a particular primer will tighten an otherwise mediocre load. All my loads are developed over a 35P Oehler chrono. I've never noted any dramatic change in velocities in changing primers. Usually in the "negligible" range of less that 20 fps, some attributable to ambient conditions. That's one reason the results posted by DB Bill were so startling to me.

Since I normally start load development with Federal primers, usually 210M's or 205M's, I have noted that velocities are usually a bit higher with the 210's than with magnum primers. Makes me wish I had strain gauges on some of the tested rifles to check pressures. I have a difficult time believing higher velocity with lower pressure. I've found not pattern to results based on milder primers. However, since I do start with what many consider a milder primer and the majority of my loads continue using them, then maybe there is a correlation.

I always start out using "benchrest-type" primers as they don't seem to blast the bullet out of the neck like some of the hotter primers do...my main concern has always been accuracy and consistency with adequate velocity to do the job. If I need more velocity I move up to a bigger case or a longer barrel.

If you have access to QuikLoad you might take a look at what changing primers (all else the same) does to barrel time for your specific load...very interesting when you are trying to find a sweet spot.

I've never run across a cartridge or powder which seemed to benefit from "magnum" primers. Ignition reliability, velocity, and accuracy all seem as good, or usually better, with "standard" primers. This has been true for me even when using very slow ball powders in very large cases. Of course, without very sensitive equipment, I have no way of knowing the relatively small differences in peak pressures or pressure curves with different primers.

I seem to recall in Ken Waters "pet Loads" for the 7mm-08 that he had a load in there which jumped dramaticaly in velocity when he switch to magnum primers. With one of the Winchester powders I believe. - Dan

I would use the CCI-250 in anything.

You guys all know your stuff. No argument.
From the posts you can see there is no rhyme or reason to this, nothing etched in stone. Runs of primers vary just as do powders, brass and bullets. How many of you have "lost" a top load in a certain rifle, never to fully restore it? There are reasons for this and these same reasons are why any of us are darn lucky to find and retain a top loading over time. When groups start to open up one day, guys start snugging up the scope mounts, checking the bedding or looking for throat erosion, forgetting all about such things as component manufacturing variables.

[This message has been edited by Nickudu (edited 01-11-2002).]