to allow us to back-calculate temperature at each measured location to the instant after the last bullet had passed. We fired all shots in the controlled environment of the Cortez, Colorado Rifle and Pistol Club, Indoor Range. To the extent possible, ambient temperature, air currents and lighting were maintained at a constant value. Greatest noted variable was ambient temperature, which we continuously monitored. I corrected all data presented here to mitigate variables associated with both variations in ambient temperature and variations in barrel temperature before we fired the first shot of each test string. We gathered sufficient data with each test to assure that only minimal errors resulted from the necessary corrections.
For each test, we recorded ambient temperature, then barrel temperature at the specified locations (above chamber – as close to the barrel nut as was feasible, at 6-inches, 12-inches, 18-inches, and 24-inches from the receiver). We then fired twenty rounds at a strict fifteen-second cadence – each shot occurred no more than +/- one-second from this interval; variation of most intervals was far less than +/- one-half second.
As noted above, fifteen seconds after firing the last shot of each string, we began the temperature reading series. We then took readings as indicated in the following table: