Quest for Less Vertical — Six Primer Types Tested at 500 Yards
Do primer types make a significant difference in accuracy or vertical dispersion at long range? The answer is “maybe”. Here’s one anecdotal study that tracked vertical variance among six different primer types. The tester is a good shooter with a very accurate rifle — four of the six 4-shot groups were under 2″ at 500 yards. This test doesn’t settle the question, but does suggest that it may be worth trying a few different primer types with your match ammo.
Here is a very interesting test for the 6 BRA (6mmBR Ackley) cartridge. Forum member James Phillips, a talented long-range benchrest shooter, tested SIX different primer types from three different manufacturers. To help determine vertical dispersion, James set his target out at 500 yards. He then proceeded to shoot 4-shot groups, in order, with each primer type. Velocities were recorded with a chrono. The photo above shows the results. James says: “I’ll retest the best two for accuracy and consistency with 10 shots each”. CLICK HERE for full-screen target photo.
As you can see, ALL the groups are pretty impressive. The smallest groups, 1.253″, was shot with CCI 400 primers. Next best (and very close) was CCI BR4, at 1.275″ for four shots. The “flat line” winner was the Remington 7.5, at upper left. There was almost no vertical. If you are intrigued by this interesting primer test, you can join the discussion in this Primer Test FORUM THREAD.
| Primer Brand | Group Size | Velocity | Extreme Spread | Std Deviation |
| Remington 7.5 | 1.985″ 4 shot | 2955 FPS | 8 FPS | 4.0 FPS |
| Federal 205M | 2.200″ 4 shot | 2951 FPS | 11 FPS | 4.8 FPS |
| Sellier Bellot SR | 1.673″ 4 shot | 2950 FPS | 14 FPS | 5.9 FPS |
| CCI 450M | 2.341″ 4 shot | 2947 FPS | 14 FPS | 6.6 FPS |
| CCI 400 | 1.253″ 4 shot | 2950 FPS | 3 FPS | 1.3 FPS |
| CCI BR4 | 1.275″ 4 shot | 2949 FPS | 15 FPS | 6.9 FPS |
CARTRIDGE: 6mmBR Ackley, aka 6 BRA. Parent case is 6mmBR Norma. The 6 BRA is fire-formed to create a 40-degree shoulder and less body taper. Capacity is increased, but the neck is longer than a 6mm Dasher. The capacity is enough to get to the 2950+ FPS accuracy node. Some shooters say the 6 BRA is more forgiving than the 6mm Dasher. The 6 BRA is certainly easier to fire-form.
LOAD SPEC: 6 BRA (40° 6 BR Improved), 31.1 grains Hodgdon H4895, Bart’s 105gr “Hammer” bullets.
TEST REPORT — Conditions, Shooting Method, Loading Method
Tester James Phillips posted this report in our Shooters’ Forum:
Conditions: The testing was done in the morning over flags. The flags never moved or even twitched. I had as perfect conditions as I could have asked for. It was overcast so no mirage and no wind. There were no other shooters, just me.
Test Procedure: Each shot was precisely shot at my pace and centered the best possible using my Nightforce 15-55X scope. I did not use the round-robin method. Each four-shot group with the same was shot at one time. Then I moved onto the next primer. Everything felt right for each and every shot fired today. Of course I could repeat the test tomorrow and it could be exact opposite of today’s test. We can chase this forever. But [soon] I’m going to test the BR4 and 400 primer… for best accuracy and consistency for 10 shots each.
How Rounds Were Loaded: Each load was weighed to one (1) kernel of powder. So I know that’s as good as I can weigh them. Each bullet seating force was within 1# on my 21st Century hydraulic arbor press.
Previous Initial Load Testing: All groups were shot with 31.1 grains of H4895. During initial load testing I settled in on the Sellier & Bellot primer to finalize everything as it showed more promise over the CCI 450 Magnum I also tried. I was actually surprised to have seen the higher ES and SD from that primer today along with the vertical shown. [Editor: Look carefully — one shot from the CCI 450 is right in the center black diamond, stretching the vertical. By contrast the Rem 7.5 had almost no vertical.]
Velocity and NODE Considerations: I was about 5-6 FPS above what appeared to been my optimum velocity of 2943-2945 FPS, so I’ll test 5 shots of 31.0 and 5 of 31.1 and see what happens from there. I can only assume my velocities where higher due to the higher humidity and of course temps were 5 degrees warmer this morning as well. It wasn’t far off but I noticed it.
Similar Posts:
- Vertical Dispersion Test — Six Primer Types Tested at 500 Yards
- Primer Comparison Testing with 6 BRA at 500 Yards
- Switching Primer Types CAN Change Pressure and Velocity
- How Changing Primers Can Affect Velocity in the .308 Win
- Long Range Load Development for F-Class
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Tags: 6 BRA, 6mm BR Ackley, BR4 Federal, CCI Primers, Federal Primers, James Phillips, Long Range Testing, Rem 7.5 Primers, Vertical Dispersion
Nice information , but the gentleman doing the test had a lacking of knowledge regarding the Rem 71/2BR primer . It has the highest brisance of any primer in comparison to those tested . And he could have dropped the powder load by .2 or .3 and gotten a much tighter group . In other words ; the 71/2 is a much hotter primer than what it was compared to . Equal powder loads don’t make for a equal primer test .
Loads must be adjusted for each primer for a proper tune.
The stated purpose of the test was to see which primer produced the least amount of vertical dispersion. The Remington 7 1/2 was the clear winner. The fact that it was the fourth largest group may have to do with other factors such as the order in which the groups were shot. Mr. Phillips says no wind. Were there wind flags placed along the entire 500 yard path of the bullet (50-100 yard intervals)? A wild guess, based on the similarity of the group shapes, that the primer test groups may have been fired in the following order: Remington, Federal, B&S, CCI-450, CCI-400 and CCI-BR4. That would also imply that the aim point was not adjusted during each 4 shot group. Perhaps Mr. Phillips will respond and clear up these questions. With the exception of the B&S primers, I have used all of these primers in various cartridges. The CCI-400 gives impressive results in PPC’s and .223 variants. In dry, warm climes such as Southern Arizona however, you may find that in temperatures above 80° your favorite load may begin to crater or pierce. CCI-400’s were designed for low capacity cartridges such as the .22 Hornet.