Shot 1 runs about 36 fps faster
21 chronograph strings from Oct 19, Oct 20, and Nov 7, 2026. Shot 1 averaged about 36 fps faster than the later shots in the same string.
The figure summarizes 21 chronograph strings of 3 to 5 shots, from Oct 19, Oct 20, and Nov 7, 2026. The rifle is a .223 Savage Axis II with a 1:9 twist, at 100 yards. The ammunition is Lapua 69 gr Scenar-L handloads, except the Oct 20 strings, which used N140 and a Berger 73 gr BT.
AI was used to plot each recorded string against the average of its own later shots, so the first-shot offset is visible instead of buried in a list. Each colored line is one string. The white line is the average, with the 95% confidence interval. The reading below was checked against the session notes.
Shot 1 averages about 36 fps faster than the rest of its string. The 95% confidence interval is about 26 to 46 fps. Shots 2 through 5 hover near zero.
The cause is unknown. A cold or clean bore, and ammunition temperature, are candidates. The planned check is a fouler shot plus warm ammunition.
These are short strings from three dates, and one date used a different bullet. The average describes this set of 21 strings.
The charges written down for these sessions are records from this rifle. They are not a recommended load. The limits are on the Safety page.