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  • Category: Shooting

Standard vs. magnum primers

 

After tearing considerable portions of hair off my head due to the velocity differences between Quickload and my trusty Chrony chronograph, I thought I´d have a go at magnum primers. There was a difference of 72 mps (236 fps) between Quickload (volume tuned to my fired cases) and reality using my Blaser R8 in 8x57IS with a 52 cm (20,5") barrel. Therefor I loaded five cartridges of each primer (CCI 200, CCI 250 and Federal 215) with all other factors the same:

Brass: Norma
Powder: 48,0 grains Norma 202 measursed with the wonderful RCBS Chargemaster Combo
Bullet: Hornady RN 170 grains
COAL: 72,0 mm / 2,835"
Distance to barrel lands: 5,6 mm / 0,22"
Chronograph: Chrony M1

I measured the weight of water that a fired case contains and using this information, Quickoad told me I´d get 782 mps / 2566 fps. The shots were fired Round Robin i.e. CCI 200, CCI 250, Fed 215, CCI 200, CCI 250, Fed 215, etc. in order to lessen the effect of barrel temperature and fouling. These were the results:

Primer Velocity mps (fps) ES SD
CCI 200 739 (2425) 17 (56) 6 (20)
CCI 250 752 (2467) 11 (36) 5 (16)
Fed 215 765 (2510) 19 (62) 6 (20)

 

So, what kind of conclusions could be drawn from this? Well, magnum primers give higher velocities than standard primers, but we already knew that - didn´t we? There is still some room up to the fantasy numbers of Quickload even when using Federal 215. Extreme spread and standard deviation seem quite ok with this limited amount of statistical foundation, and then there´s the tolerance and uncertainty of the chronograph also. But all in all a fairly interesting result, for what it´s worth.