Mother of All LR Primer Tests
If you shoot a .308 Win, or any cartridge that uses a Large Rifle (LR) primer, you should read an important article by Laurie Holland in Target Shooter Magazine. Holland, a talented shooter from the UK (and Accurate Shooter Forum member), tested no less than sixteen (16) different large primer types using a custom F-TR target rifle shot from the bench. Laurie loaded .308 Win ammo* with 16 LR primer varieties and then tested for average velocity, ES/SD, and group size. This may be the most comprehensive and thorough LR primer test ever done. Here are the primer types tested:

LINK: READ Large Rifle Primer Test Complete (16 Primer Types)

Test Rig: Osprey Rifles-built F-TR rifle with Savage PTA action, 32″ Bartlein 1:12″-twist ‘Heavy Palma’ barrel, and Dolphin Gun Company modular stock with an F-Open/Benchrest fore-end.

Some of Laurie’s results may surprise you. For example, would you guess that Sellier & Bellot primers had the lowest ES, by a significant margin? And get this, among ALL the primers tested, Rem 9½M Magnum primers produced the lowest velocity, while Rem 9½ LR (non-magnum) primers yielded the highest velocity. (The total velocity spread for all primers was 35 fps). That’s counter-intuitive and it’s odd that Rems were at opposite ends of the speed spectrum among ALL primers tested.

“The rationale for doing side-by-side tests is to see what effect primer choice has on ballistics, i.e. average velocities and MV consistency. There are a great many views on the subject, a few based on tests (including primer flame photography) but most apparently hearsay.” — Laurie Holland

Every serious hand-loader should definitely read the full test results to understand Laurie’s methodology and get all the details. This is an important test, with significant findings. But if you can’t spare the time right now, here are some highlights below:

Primer with Lowest Velocity: Remington 9½ M Magnum (2780 fps)
Primer with Highest Velocity: Remington 9½ LR (2815 fps)
Primer with Lowest ES/SD: Sellier & Bellot LR (12/3.1 fps)
Primer with Highest ES/SD: Remington 9½ M Magnum (47/14.0 fps)
Primer with Smallest Group Size: Remington 9½ LR (0.43″ average, three 5-shot groups)
Primer with Biggest Group Size: CBC Magtech 9½ (0.7″ average, three 5-shot groups)

Editor’s Comment: Laurie shot three, 5-shot groups at 100 yards with each primer type. The average group size for the top six primers varied by only 0.10″ (0.43″ to 0.53″), so one can’t conclude that one type is much better than another. Total group size variance (from best to worst) was 0.27″.

“The biggest surprise to me … came from an elderly (at least 10 years) lot of Czech Sellier & Bellot standard caps with an ES of 12 and SD of 3.1 fps, way below those of the nearest competitor. By contrast to the Fiocchis, they were an almost slack fit in the cases and this may have contributed to their consistent performance.” — Laurie Holland

NOTE: Values in chart are based on 15-Shot strings. The ES/SD numbers will therefore be higher than is typical with five-shot strings.

All ES/SD Values from 15-Shot Strings

Testing 16 primer types was a huge task — we commend Laurie for his hard work and thoroughness. This extensive test is an important contribution to the “knowledge base” of precision shooting. Laurie’s findings will doubtless influence many hand-loaders who hope to produce more consistent ammunition, or achieve better accuracy. Credit should also be given to Target Shooter Magazine for publishing the results. Well done gentlemen…

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 ask join the discussion in this Primer Test FORUM THREAD.

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.