01-20-2020, 12:34 AM
"Temperature sensitive" refers to how much gain or loss of velocity a round with that powder will have, per degree F of temp. So if a powder is sensitive, that usually means 1.0 ft/sec per deg F muzzle velocity (MV) or more.
CFE 223 powder is listed in several places as being 1.0 ft/s/*F, Varget (not very sensitive) is more like 0.19 ft/s/*F. RL-15 is 1.52, very sensitive.
So for example, if you load rounds at 72 *F (as in your workshop) with CFE223 at a "max" for you barrel then go outside to hunt in 20 *F winter temperatures, you could expect a drop of about 50 ft/s in your MV... So a 123 gr bullet that you think would shoot at 2475 ft/s (what you loaded for, max for your gun) might actually fire off in that wintry weather, at 2425 ft/s. Your point of impact, downrange energy, ballistics and even accuracy might well suffer because of that drop in MV.
Or, load it "safely (you think)" at 72 *F then go out to shoot in 110 *F summer weather... The resulting load could be too hot and have an overpressure situation due to firing at a MV of ~2500 ft/s... which could be too much for your barrel.
CFE 223 powder is listed in several places as being 1.0 ft/s/*F, Varget (not very sensitive) is more like 0.19 ft/s/*F. RL-15 is 1.52, very sensitive.
So for example, if you load rounds at 72 *F (as in your workshop) with CFE223 at a "max" for you barrel then go outside to hunt in 20 *F winter temperatures, you could expect a drop of about 50 ft/s in your MV... So a 123 gr bullet that you think would shoot at 2475 ft/s (what you loaded for, max for your gun) might actually fire off in that wintry weather, at 2425 ft/s. Your point of impact, downrange energy, ballistics and even accuracy might well suffer because of that drop in MV.
Or, load it "safely (you think)" at 72 *F then go out to shoot in 110 *F summer weather... The resulting load could be too hot and have an overpressure situation due to firing at a MV of ~2500 ft/s... which could be too much for your barrel.
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