Written by Sierra Bullets Ballistic Technician Robert Treece
Printing deadlines for the latest reloading manual kept us from working up specific data for .30 caliber gas guns, as was intended.
Note that barrel lengths for most gas guns are usually shorter than the “bolt gun” test firearm used, so velocities will be lower and affect trajectory!
Starting out, you need to reduce all the data by one full grain if thicker military cases are being used, unless they are National Match cases. National Match cases have about the same interior volume as commercial brass. I also wouldn’t recommend using the max “adjusted” charge so as to be easier on operating rod.
With your floating firing pin, use a hard cupped primer to give best odds of NOT having slam fires. One “squirt” of slam firing will ruin your shorts and makes everyone near you on firing line “have a little pucker time!” Reputation indicates that the CCI brand primers are predicted to have hardest cups with the #34 (a magnum intensity cap like their 250 and recommend reduction of another grain of powder in loads) being first choice.
Browning BAR’s can use most of the powders listed—all others should work with medium fast propellants like the 4895’s, 4064’s and others in that burn rate range.
Hope this helps—good shooting and thanks for using our products!