How many rounds for reliable chronograph data?

[thefitter]

How many rounds do you shoot to get reliable ES & SD chronograph data?

 

[bheadboy]

this will most likely cause lots of conversation, but for my purposes, (some non com target, pd, hunting) i use the same 5 cases and load them carefully 3 times using the same stuff, then average and look for flyers.look for consistancey and if not then change one thing at a time


bob

 

[Keith Glasscock]

Typically, a 10 shot string is used.

While 10 isn't statistically super-duper, the error margin has reduced enough to give a decent idea of what is going on. Longer strings would give a greater confidence in the data.

ES is a funny thing, it only tells us how far the fastest is from the slowest. In other words, one bad reading or light charge can really goof things up.

For my money, I shoot multiple strings across the chrono on different days (from different loading sessions) and average the SD and ES. From that data, I can derive information about the expected performance of the ammunition. I always have to validate my data by actually shooting at the desired range. If it groups good and consistently there, all is well.