June 25th, 2020

Quest for Less Vertical — Six Primer Types Tested at 500 Yards

primer 500 yard testing node vertical H4895 BRA

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.

Wheeler 6BR 6mmBR Ackley Improved James Phillips

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.

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.]

primer 500 yard testing node vertical H4895 BRA

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.

Permalink Bullets, Brass, Ammo, Competition, Tech Tip 3 Comments »
June 25th, 2020

Incipient Case-Head Separation — How to Detect the Problem

cartridge case separation

We are re-publishing this article at the request of Forum members who found the information very valuable. If you haven’t read this Safety Tip before, take a moment to learn how you can inspect your fired brass to determine if there may be a potential for case separation. A case separation can be dangerous, potentially causing serious injury.

cartridge case separationOn the respected Riflemans’ Journal blog there was an excellent article about Cartridge Case-Head Separation. In this important article, Journal Editor GS Arizona examined the causes of this serious problem and explained the ways you can inspect your brass to minimize the risk of a case-head separation. As cases get fired multiple times and then resized during reloading, the cases can stretch. Typically, there is a point in the lower section of the case where the case-walls thin out. This is your “danger zone” and you need to watch for tell-tale signs of weakening.

The photo below shows a case sectioned so that you can see where the case wall becomes thinner near the web. You can see a little arrow into the soot inside the case pointing to the thinned area. This case hadn’t split yet, but it most likely would do so after one or two more firings.

cartridge case separation

Paper Clip Hack for Detecting Problems
The article provided a great, easy tip for detecting potential problems. You can use a bent paper clip to detect potential case wall problems. Slide the paper clip inside your case to check for thin spots. GS Arizona explains: “This simple little tool (bent paper clip) will let you check the inside of cases before you reload them. The thin spot will be immediately apparent as you run the clip up the inside of the case. If you’re seeing a shiny line on the outside and the clip is really hitting a thin spot inside, it’s time to retire the case. If you do this every time you reload, on at least 15% of your cases, you’ll develop a good feel for what the thin spot feels like and how it gets worse as the case is reloaded more times. And if you’re loading the night before a match and feel pressured for time — don’t skip this step!”

Permalink Bullets, Brass, Ammo, Reloading 2 Comments »
June 25th, 2020

Save $20 on MagnetoSpeed Sporter Chronograph — $159.99

Magnetospeed sporter MidwayUSA chron chronograph

This post essentially puts twenty bucks in your pocket if you need a chronograph. You see the MagnetoSpeed Sporter Chrono typically costs around $179.00 from most vendors. But right now MidwayUSA is running a special — the true “shopping cart price” is $159.99. That’s $20.00 cheaper than Midway’s regular price, and $19.01 cheaper than the lowest price we found anywhere else. But this special “Shopping Cart Discount” may not last long, so you may want to act quickly. We confirmed Midway’s $159.99 price on the morning of June 28, 2019.

Strapped on your barrel, the MagnetoSpeed Sporter records velocities accurately without requiring any hardware to be placed downrange. Everything is self-contained at your shooting station, so you no longer have to waste time setting up tripods and aligning the bullet path through old-fashioned chrono skyscreens. For most shooters, the MagnetoSpeed Sporter is all they need — they don’t need to spend $380.00 for the Deluxe MagnetoSpeed V3 Model. Here’s a video review which compares the Sporter to the more expensive V3 chronograph.

Permalink Gear Review, Hot Deals No Comments »