I've been sorting primers by weight on my ELR stuff for a while. My thoughts are it matters less with the larger cases but much much more with deep transonic distances. The only comparisons I've done with those cartridges is sorted vs. unsorted. There is a consistent small drop in an already low SD. For another 20 minutes per hundred in a process where I handle each piece of brass a couple dozen times, I'll take it. I do a brick of 1000, then load with similar weights.
The last couple threads introduced what I thought were good ideas on making the primer weight impact on velocity pop out above the noise. Those were smaller cases and testing the heaviest against the lightest. I have a 223 I use for long distance practice. It's a 26" 1:7 Bartein with a Wylde chamber that's been throated to load 75 grain ELDm to 2.500". Bought new Lake City brass loaded with 24.5 grains of H4895 gives 3030 fps. The emphasis for this ammo is balancing the effort and cost with the results. The 500 count was weight sorted into batches of 100 with similar weights initially, but no subsequent sorts. No neck turning. Moving the bullet forward in the neck captures a significant chunk of the velocity spread benefits that would have been seen with neck turning.
I had a batch of 50 that were last used to test 5 different loads involving 3 bullets and 2 powders. Because the pressure histories on them were different, I checked their volume with alcohol after trimming and sizing. This gave 20 with the same volume and 10 more with 0.1 grain of water less.
1000 Fed 205MAR primers were sorted using an A&D FX120 on the gram setting. This was my first sort using the gram setting. I'm not convinced it added any precision to the measurement. I test a few primers to find one that looks close to the middle of the distribution and zero the scale with it. It's set aside for use rezeroing the scale during the process. The variation in weight went from +5 to -4 milligrams. Out of 1,000 there were no +1 or -1 samples. About 2/3 of the primers were the same weight as the one selected as the zero.
I loaded up the 10 heaviest, 10 lightest, and 10 from the middle with my standard 223 load.
This wasn't a single topic for YouTube test. I recorded the velocities as I shot the normal COF I use for entertainment. That is 2/3 IPSC and 10" gongs ridge to ridge at 750 yards. So no groups. No sighters in this game so I'm in the habit of measuring and recording the ammo temperatures before it's shot. The ammo temperature is used to guess what todays average is going to be before it happens.
The results were:
+3 to 5 mg
3038, 22.4, 8.2 with 55 F ammo
-3 to-4 mg
3020, 18.4, 5.2 with 61 F ammo
0 mg
3039, 19.4, 6.4 with 65 F ammo
My baseline for this load is 3030 fps with 60 degree ammo. Velocity changes 3/4 fps per degree. 3/4 means more than 0.5 and less than one.
Primer weight, Heavy, Zero, Light
Observed velocity, 3038, 3039, 3020
Temperature Corrected velocity, 3042, 3035, 3019
A 10 shot string of the standard production loading gave:
3027, 26.3, 7.9 with 61 F ammo.
This was 10 good ones. Typical values are 3030, 27ish, ~9
No primer sorting, no additional brass weight or volume checks after the initial sort.
Am I going to start sorting primers for my practice ammo? No.
Low velocity spread 223 is something of a white whale for me though. I might fire up the Bison case volume tool to select 100 cases to use those sorted primers in. That ammo would only be used for special occasions.
I think I will use this basic test when I sort a lot of primers for use in the larger cases. It looks like a straightforward way to improve the signal to noise ratio. After enough tests, the consistency of the results will be easier to judge.
- Al
