Many of the loads listed in most reloading manuals call for magnum primers. With the great shortage of primers and other components, you may find yourself short on magnum primers. we did a small test to see what the difference would be if standard primers were used instead of magnum primers. Obviously if a powder used is one that is hard to ignite, magnum primers are going to be required. Most of the current powders that are appropriate for pistol and revolver loads are not going to be especially hard to ignite. Before we get to the test that we did, it needs to be stated that if you substitute magnum primers for standard primers, the powder charge must be reduced and the load worked up to make sure that the load is not over pressure. Using Standard primers in place of magnum primers is going to generally result in at least somewhat lower pressure.

CAUTION

The information in this article is not promoting indiscriminate substitution of components. Use published data from reliable sources. Since Craig’s Outdoor Sports has no control over any information in this article, we are not responsible for any use of this information.

Putting Our Test Together

For our test of substituting standard primers for magnum primers, we used the 357 Magnum. New Starline cases were chosen. The cases were measured and chamfered. The length of all the cases in the lot that we got were all spot on, so no trimming was required. 50 cases were then primed with CCI 500 small pistol primers and the other 50 were primed with CCI 550 small pistol magnum primers. The powder that we selected was Hodgdon H110. Bullets used were 180 grain lead, round nose, flat point, from Missouri Bullet Company. We used the bullets with the polymer coating that Missouri Bullet Co. is using on some of their bullets. Each powder charge was weighed to keep as many variables as possible to a minimum. Bullets were seated and then crimped in separate operations. All loads were assembled with the only change being the primer used. All the loads were fired from a Colt Single Action Army with a 5 1/2 inch barrel across a ProChrono chronograph.

Results of Test

Loads with magnum primers averaged 1070 FPS. The highest velocity was 1106 FPS and the lowest was 1015 FPS giving 91 FPS deviation. This load is the starting load published for the bullet used.

The same load with the standard primers gave a top speed of 1059 FPS and a low of 824 FPS for a deviation of 235 FPS. The 824 FPS low seemed to be an anomaly, as most of the rounds fired were 100 or more FPS faster. However, even if the lowest round was not counted, the standard primer load has some more deviation than the magnum primer loads. All rounds fired functioned flawlessly and showed no issues. When these loads were fired at a 6 inch steel plate there was no noticeable difference noted. If I was after top velocities and had a load that is listed with magnum primers, I would choose to use magnum primers. However, substituting standard primers when those are what I have available does not create a huge disadvantage.