Means you are working with a powder that with a heavier bullet is going to be more peaky, more sensitive and with powder charge varying that much, can get you into a high(er) pressure situation.
Krieger bbls then do run tight on land and groove diameters, not crazy tighter but tighter. That bumps up pressure.
Shorter freebore chamber (223 vs Wylde vs NATO), tighter barrel, powder charge variation on high side, add that maybe round sat in chamber for a longer period of time....all adds up to pressure increase. Maybe a case that was a bit softer than should be due to a process error or ???.
Pressure isn't linear, especially on higher side of curve. Gets even more interesting if running a double base powder and running it on high side of pressure.
I prefer single base, extruded powders but see appeal to double base. Sometimes the only way to get "there" is to run a double base. One just has to keep in mind that it isn't good to push double base hard, then use that same ammo when 30-40 degrees warmer.
Case # | Charge weight - grains | Abs Deviation - grains |
7 | 21.8 | 0.555 |
4 | 21.9 | 0.455 |
6 | 21.9 | 0.455 |
10 | 21.9 | 0.455 |
8 | 22 | 0.355 |
9 | 22 | 0.355 |
5 | 22.2 | 0.155 |
3 | 22.3 | 0.055 |
13 | 22.3 | 0.055 |
18 | 22.4 | 0.045 |
15 | 22.5 | 0.145 |
17 | 22.5 | 0.145 |
20 | 22.5 | 0.145 |
1 | 22.6 | 0.245 |
2 | 22.6 | 0.245 |
12 | 22.6 | 0.245 |
14 | 22.6 | 0.245 |
16 | 22.6 | 0.245 |
19 | 22.6 | 0.245 |
11 | 23.3 | 0.945 |
| | |
| Average - grains | 22.355 |
| | |
| ES - grains | 1.5 |
| | |
| Standard Deviation - grains | 0.355633238 |
| | |
| Mean Average Deviation - grains | 0.206554472 |
Name of precision (ammo, optics, shooting, etc) is to have it be the same each time, when precision isn't there, "interesting" things can happen.
Pressure wise, that's really hard to guesstimate as it would depend heavily upon where you are on curve for the average charge.
Depends on what barrel and chamber the ammo was tested / developed in also. Lotta variables to account for to be able to say much of anything useful.
Powder charge variation is bad. Powder charge variation with faster burn rate powder, combined with bullet that is "heavy" for cartridge is even worse.
Internal ballistics - it'll give you a headache, one way or another.