Temperature and humidity effects

[ArcherAdam]

Really becoming interested in handloading now. What is your experience with temperature and humidity when shooting? Does one open up groups or effect accuracy? I know shotgun patterns can be effected by both? Obvioulsy I would want to shoot in similar conditions when testing loads but that may not always be an option. I would like to give each round a fair chance! Thanks! AA

 

[DrMike]

There is a measurable effect of temperature on accuracy; however, for all practical purposes, the effect will prove negligible. Some powders are more temperature sensitive than are others. If this is a concern, choose to work up your load with one of the powders that are marketed as less temperature sensitive (e.g., Hodgdon Extreme powders). Humidity appears to be less of a concern as the propellant and primer are effectively a closed system. They are, however, not immune to temperature fluctuations. Hence, there is a measurable, though negligible, effect of temperature on burn rates.

 

[Ridge_Runner]

the difference in POI at 1000 yards is less than 2" from zero percent humidity to 100 percent
RR