Round count

[ultrablue]

How many rounds should be fired for a chrono session?

[Dwain C. Baer]

How many rounds should be fired for a chrono session?

At matches usually three to four rounds. However, if you're testing reloads, perhaps one or two magazines worth.

[bbbean]

Test enough ammo to trust your numbers. If I'm working up a new load, I need at least two runs of 20 rounds that make power factor with a safe margin. This means that the slowest 7 rounds make power factor, and the run of 20 is at least 1.5 standard deviations above 165. If I'm checking a known load before a major, one run of 20 will do, assuming it checks out.

[KyroWebs]

If I am just starting to work a load up I'll do 5 or 6 just to see approximately where I'm at. Once I get to my desired velocity I'll do 30 rounds. If my avg velocity - 3SD will give me PF above 167(major) or 127(minor) I am happy.

Edited August 30, 2011 by KyroWebs

[Dwain C. Baer]

If I am just starting to work a load up I'll do 5 or 6 just to see approximately where I'm at. Once I get to my desired velocity I'll do 30 rounds. If my avg velocity - 3SD will give me PF above 167(major) or 127(minor) I am happy.

Sounds like a good plan...

[ultrablue]

Thanks folks. Sounds like between 20 and 30 for a good evaluation of PF.

[RePete]

I use 10rds for pistol and 5 for rifle.

[blueeyedme]

When developing rounds, I load of 10 of each to test functionality and hone in on my velocity target. For final testing I bracket the velocity target and load 30 rounds of each - 20 for the chrono and 10 to test accuracy before I go into production with my final selection.

[StravIs09]

sounds like a big waste of ammo to shoot 30 X multiple loads you are testing.

not saying its a bad thing to get you load 100%. but i dont play it that close making my load right on the 165 pf major minimum. I load to 170+ if it doesnt make 170 avg on 5 shots then you got to go back and try some more powder. dont be afraid to shoot ammo at 172-175pf.

[Skydiver]

5 shots gives you a good idea of what the average is. Usually a test population of 20-30 gives you a very good idea of your standard deviation.

[bbbean]

sounds like a big waste of ammo to shoot 30 X multiple loads you are testing.

not saying its a bad thing to get you load 100%. but i dont play it that close making my load right on the 165 pf major minimum. I load to 170+ if it doesnt make 170 avg on 5 shots then you got to go back and try some more powder. dont be afraid to shoot ammo at 172-175pf.

It makes perfect sense if:

1) You want to be completely relaxed in the chrono tent, and

2) You understand the potential of a combination of outliers, production variability, and Murphy's law.

BB

[motosapiens]

sounds like a big waste of ammo to shoot 30 X multiple loads you are testing.

not saying its a bad thing to get you load 100%. but i dont play it that close making my load right on the 165 pf major minimum. I load to 170+ if it doesnt make 170 avg on 5 shots then you got to go back and try some more powder. dont be afraid to shoot ammo at 172-175pf.

It makes perfect sense if:

1) You want to be completely relaxed in the chrono tent, and

2) You understand the potential of a combination of outliers, production variability, and Murphy's law.

BB

I suspect that being relaxed in the chrono tent has more to do with faith than with statistics and probability. I'd rather test 5-10 rounds each at 3-4 different chrono sessions than 30 all at once, but that's how my faith works. USPSA chrono procedures are pretty forgiving. ymmv.

Edited March 6, 2012 by motosapiens