Changing Primer Type CAN Alter Pressure and Velocity

We are often asked “Can I get more velocity by switching primer types?” The answer is “maybe”. The important thing to know is that changing primer types can alter your load’s performance in many ways — velocity average, velocity variance (ES/SD), accuracy, and pressure. Because there are so many variables involved you can’t really predict whether one primer type is going to be better or worse than another. This will depend on your cartridge, your powder, your barrel, and even the mechanics of your firing pin system.

BE SAFE: Be cautious when changing primer types. Glen Zediker recommended decreasing your load ONE FULL GRAIN when changing to a different primer type, one that you haven’t used before.

Interestingly, however, a shooter on another forum did a test with his .308 Win semi-auto. Using Hodgdon Varget powder and Sierra 155gr Palma MatchKing (item 2156) bullets, he found that Wolf Large Rifle primers gave slightly higher velocities than did CCI-BR2s. Interestingly, the amount of extra speed (provided by the Wolfs) increased as charge weight went up, though the middle value had the largest speed variance. The shooter observed: “The Wolf primers seemed to be obviously hotter and they had about the same or possibly better ES average.” See table:

You can’t extrapolate too much from the table above. This describes just one gun, one powder, and one bullet. Your Mileage May Vary (YMMV) as they say. However, this illustration does show that by substituting one component you may see significant changes. Provided it can be repeated in multiple chrono runs, an increase of 19 fps (with the 46.0 grain powder load) is meaningful. An extra 20 fps or so may yield a more optimal accuracy node or “sweet spot” that produces better groups. (Though faster is certainly NOT always better for accuracy — you have to test to find out.)

WARNING: When switching primers, you should exercise caution. More speed may be attractive, but you have to consider that the “speedier” primer choice may also produce more pressure. Therefore, you must carefully monitor pressure signs whenever changing ANY component in a load. In his books, the late Glen Zediker recommended decreasing your load ONE FULL GRAIN when changing to a different primer type, one that you haven’t used before.