Changing Primer Types Can Alter Load Velocities and Pressures
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.
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:
| 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 |
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. Glen Zediker recommends decreasing your load ONE FULL GRAIN when changing to a different primer type, one that you haven’t used before.
Similar Posts:
- Changing Primer Type CAN Alter Pressure and Velocity
- Yes Both Velocity and Pressure Can Vary with Primer Choice
- How Changing Primers Can Affect Velocity in the .308 Win
- Primers and Load Velocity: CCI-BR2 vs. Wolf in .308 Win
- Switching Primer Types CAN Change Pressure and Velocity
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Tags: .308 Win, BR-2, CCI, Federal, Pressure, Primers, Varget, Velocity, Wolf
I thank you and your readers for an appetite for this type of experimentation. In the long run it will benefit all of us. The data presented here has little value if it’s given without the number of samples taken or the standard deviations. There is no way to determine if this is statistically valid or just random noise.
I make decisions of the basis of small sample tests all the time. If, on a given day, I find that some load change reduces the size of my groups, I tend to believe the targets. I am familiar with statistics, and also know that some fellows can become so preoccupied with what they have learned about them, that they completely loose sight of what is practical. We all make decisions, all the time based on anecdotal evidence that would not pass muster for any sort of scientific study, and by and large the process works. If someone wants a larger sample, no one is preventing him from gathering the information, but I seldom see any published data from those who nit pick numbers.
I think if your load is within 20 fps of being over pressure its to hot to start with. Interesting read though.
Mr. Allen – please tone down the sneering a bit and make the internet a more friendly place. As you point out
“We all make decisions, all the time based on anecdotal evidence that would not pass muster for any sort of scientific study, and by and large the process works.” This is called convenience, or faith. It’s not science as you also point out. Since you seem to agree with reader Josh, you could be nicer.
Change anything and results are likely to be changed to some degree in some place. Thankfully I don’t worry about 15-25 fps swings in velocity. The amount of work you guys put in is amazing. I just load them up the same way all the time and shoot. They hit where I aim so that is good enough for me lol. Long live silhouette shooting as I don’t think I what it takes to be a BR guy.
I tend to agree with Josh. Putting up data on the web is great, and we are all free to interpret our own results how we wish, but when we post it for others use and we draw conclusions based on that data (as in this case), it a best practice to include some details, such as number of shots, SD, and equipment used to measure. That way the reader can know how much confidence to put in the conclusion for their own use. Doing this would improve the overall practice of posting data. PRSBlog is a good example of best practice. In the case of this article, I understand that it just a topical blurb (and that the data cited was not really necessary to make the point). The author does a good job pointing out the more important fact that YMMV as they say.
I think we might have missed the point of the article , while getting into the “weeds” regarding the data , itself . What I got reading the topic was to point out that changing any individual component , particularly the primer , could be potentially dangerous . And we ; as a group , should be cognizant of that . While many here have been shooting and reloading for decades , there are also many new reloaders out there who are totally un-aware that changing a primer brand could have devastating effect , if they are already loading to a near max load . The data was anecdotal to show viable change , and little more , in my mind .
Laurie Holland did a similar but much more extensive testing of both small and large rifle primers , and some of the findings were published on this site awhile back .For those who are into “statistical analysis” , those articles cover the subject in much greater detail , and the methodology seemed very sound .
Very interesting information. Never thought that primer Can affect velocity and pressure.