Primer Test by Accurate Arms

Ambrose

I found an interesting article in the Summer, 2012 issue of The Varmint Hunter magazine. The text is by M. L. McPhearson. The test involved the .30/06 cartridge with the Sierra 168 gr. Match King and 58 gr. of A4350 together with primers including large pistol primers. The pressures ranged from a low of 53,100 PSI to a high of 63,900 PSI! with the velocity at 2827 fps to 2,951 fps. I was surprised to see the WLRM and the WLR producing more velocity and pressure than the Fed. 215. I had always thought the 215 was the hottest large rifle primer. While I felt these primers were on the milder side, I was also surprised to see the CCI 200 and the Rem. 9 1/2 near the bottom of the list along with the large pistol primers.

I have most of the primers used in the test on my shelves and use them, more or less, interchangeably. I tend to use the CCI 200 or the Rem. 9 1/2 in smaller capacity cases like the .300 Savage and the WLR for cartridges like the .270 or .30/06 but I have no hard/fast rule. I may have to re-think that. I generally use the WLRM or the 215 in magnum capacity cases but will use the CCI 250 or the Rem. 9 1/2M, too. However, the test indicated the 250 and the 9 1/2M to be kind of middle-of-the-road; milder even than the CCI 350 pistol primer!

The author claimed to use pistol primers in .30-30 class cartridges. I have read of using pistol primers in .22 Hornet cartridges to improve accuracy but this is the first time I've read of pistol primers in the .30-30. There's a lot here to think about.

If you get a chance, get a copy of this magazine and see what you think. I've put a copy of the test in a prominent location in my reloading room.

Rocky Raab

What is important to note is that "hotter primer" doesn't always translate to more velocity, or more pressure.

THE lesson to be learned is that changing primers indiscriminately is very risky. Nobody can predict what the result will be.

XXCross

When one takes into account that large pistol primers are shorter in height than large rifle primers, that looks like the potential for ignition problems. I would would not advise anyone to use LP in place of LR ...just bad policy.

v35

Proper firing pin protrusion being on the order of .061, and pretty loose headspace about.010, a .050 primer indent should be plenty.

Ambrose

Rocky; I probably shouldn't have used terms like "hotest" and "milder" primers. I was trying to indicate the location on the list of certain primers re: higher or lower pressure/velocity.

Please note that this test was not run by an individual but by the Accurate Arms Ballistics Laboratory.

Rocky Raab

There have been many such tests run. I did one myself years ago, using a known consistent load in .308 for large rifle primers and another in .223 for small primers. I ranked primers based on velocity delivered, and my "hottest" to "coolest" list is almost identical to Accurate's.

I didn't measure pressure, though. Lab results show that changing primers can cause large changes in pressure (in EITHER direction) without a large change in velocity. Different cartridge/bullet/powder combinations can have opposite results with a primer change, too. That's why it is always risky to indiscriminately swap primers.