SD and velocity observations across CCI primers

[EchoDeltaSierra]

Fine Sunday morning to all. After reviewing from testing a variety of primers in my ARC Nucleus action, I’ve noticed some interesting data that I wanted to present for discussion.

I’m loading the following 6.5 Creedmoor loads using consistent charges of H4350 and 140gr ELD-M bullets. I am using Nosler brass with large primer pockets and Lapua brass with small primer pockets, all prepped similarly and annealed after each firing. I tested CCI BR-2, 250, BR-4, and 450 primers. Charges were measured across 5-shot groups charged at the same time with each primer (e.g. 43.0 grains in Nosler brass w/ BR-2, Nosler brass w/ 250, Lapua brass w/ BR-4, Lapua brass w/ 450). Also, all loads were shot in 15-20 deg. F temps and measured with a magnetospeed.

Across the CCI primers, BR-4 primers were consistently the lowest SDs (all groups were single digit). 450 and BR-2 primers were similar SDs (5-11 measured), 250 primers were the highest SDs (12-16 range).

Velocities between BR-2 and 250 primers in Nosler brass showed the 250s about 5 FPS faster. Velocity between BR-4 and 450 primers shows the 450s are about 10-15 FPS slower than the 450s.

I thought this was interesting and am curious others’ thoughts about said observations.

 

[AIAW]

I am a fan of the Lapua BR-2 combination myself.

Just curious though - did you perhaps measure H2O capacities across of all of the brass before the testing? You could have false information with even the smallest capacity deviation even on the same headstamp, obviously.

 

[dirthead1]

Across the CCI primers, BR-4 primers were consistently the lowest SDs (all groups were single digit). 450 and BR-2 primers were similar SDs (5-11 measured), 250 primers were the highest SDs (12-16 range).

Velocity between BR-4 and 450 primers shows the 450s are about 10-15 FPS slower than the 450s.

I've tried BR4's and 450's in Lapua 6.5 Creedmoor brass and my observations mirror yours almost exactly (if your above statement is that 450's are 10-15 fps slower than BR4's).

 

[EchoDeltaSierra]

Just curious though - did you perhaps measure H2O capacities across of all of the brass before the testing? You could have false information with even the smallest capacity deviation even on the same headstamp, obviously.

Considering I’m consistently producing reliable single-digit SD ammo for PRS shooting, I’ve never messed with sorting brass... and I’m not sure that be worth the return on time. I wanted to test ignition reliability in cold weather on my new action and figured it might be an interesting way to gather data with my brass set and primers that were sitting around. This was consistent observations with 5-shots at 5 different charges across two brands of brass each with the two different primers (100 rounds total).

 

[EchoDeltaSierra]

I've tried BR4's and 450's in Lapua 6.5 Creedmoor brass and my observations mirror yours almost exactly (if your above statement is that 450's are 10-15 fps slower than BR4's).

That is my statement; 450s appear SLOWER than BR-4s. That said, 250s appear FASTER than BR-2s.

 

[dirthead1]

That is my statement; 450s appear SLOWER than BR-4s. That said, 250s appear FASTER than BR-2s.

That's exactly what I've seen with BR4's vs 450's. BR4's are lower SD and slightly higher velocity. I just wish the BR4's were a little cheaper....

 

[ShtrRdy]

I wish you would have used the same brass, along with the same bullets and powder.

I ended up using the CCI 450 in my small primer 6mm Creedmoor Lapua brass.