We are often asked, “Can I increase my velocity by changing primer types?”. The answer is “maybe”. It is important to understand that changing primers can affect your load’s performance on many levels — velocity average, variance in velocity (ES/SD), pressure, accuracy, etc. There are too many variables to predict which primer will be better. This will depend upon your cartridge, powder, barrel, and even your firing pin system.
BE SAFE: Be careful when changing primer types. Glen Zediker recommends reducing your load by ONE FULL GRAIN if you are switching to a primer type that you haven’t used before.
A shooter on a different forum conducted a test using his.308 Win Semi-Auto. Using Hodgdon Varget Powder and Sierra 155gr MatchKing Bullets, he found Wolf Large Rifle Primers to have slightly higher velocities. The amount of extra speed provided by the Wolf primers increased as the charge weight went up. However, the middle value showed the greatest speed variance. The shooter noted: “The Wolf primers appeared to be clearly hotter and had about the same, or possibly better ES Average.” See table.
Varget.308 Load
45.5 grains
46.0 grains
46.5 grains
CCI BR2 Primers
2751 fps
2761 fps
2783 fps
Wolf LR Primers
2757 fps
2780 fps
2798 fps
Speed Delta
6 fps
19 fps
15 fps
The table above is not very useful for extrapolation. This table is for a single gun, a single powder, and a single bullet. As they say, Your mileage may vary (YMMV). This illustration shows that you can see significant differences by substituting a component. If you can repeat the chrono run multiple times, a 19 fps increase (with a 46.0 grain powder charge) is significant. A 20 fps increase may result in a better accuracy node, or “sweet spot”, that produces better groups. (Although faster is not always better for accuracy – you need to test it to find out.
WARNING: Be careful when switching primers. It may be tempting to choose a primer that is “faster”, but you must also consider the fact that this may produce more pressure. You must therefore carefully monitor pressure signals whenever you change ANY component of a load. Glen Zediker, who died in 2007, recommended that you decrease your load by ONE FULL GRAIN if you are switching to a primer type that you have never used before.
