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.
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.