Colt 61 Navy by Uberti.

[mec]

sorry. Difference between highest and lowest reading over the chronograph. With most of these loads, I clock six rounds though ten or twelve would be more significant. Several batches of six rounds does add up though and gives you and idea of how consistent your loads are.

Today, I loaded all six chambers with a dose of pyrodex p from a measure that would throw 15 grains of fffg. This was behind a 110 grain bullet from one of the replica moulds. Velocities were 793, 808, 824, 818, 829, 816. Extreme spread was 36 which isn't at all bad. Alarm bells would have gone off it one had been way off like low- 793; High-900.

 

[Leatherbark]

Not Mec here ,but "Extreme Spread" is the difference between the highest velocity shot and the lowest in a string of shots placed across the chronograph.Used to measure consistancy of the load being used.....You will see the term "Standard Deviation" from time to time and it means and anyone correct me if I'm wrong that SD is how much each individual shot deviates from the other on average............Bob

 

[mec]

That sounds right to me. I record standard deviation if I shoot ten or more rounds. It really doesn't have much significance until you get into really big numbers though.