Chronographs, and figures and such...

[IronKnees]

I'm a little curious. When using your chronograph, what numbers do you consider good, average, or unacceptable? I have always considered an extreme spread of around 2 1/2 to 3% to be the maximum. I have had some rounds that shot quite well with extreme spreads over that mark, but in general, after testing loads in 0.5 grain (powder) increments, I have been able to arrive at extreme spreads of 2.0% or below. An example is a load I tried just today. There were ten shots over the chronograph, and the average velocity yielded 2187.03 fps. The high was 2225.45 fps, and the low shot was 2164.16 fps, for an extreme spread of 61.29 fps. Since this load produced a 1/2 inch group, I am very happy with it, but again, am curious as to what "numbers" some of you guys look for in your testing... Thanks... Dave

[Questor]

It depends on the cartridge.  For bottleneck cartridges, I expect a very low extreme spread-- like 25fps-- because I know I can get it if I find the right load.  With low pressure cast bullets for about 800fps, I like to see an extreme spread of under 50fps. Mostly, I use the chronograph to help me confirm whether my load matches the load data.  I've found the Speer manual to be very close-- probably because they use real guns, Nosler is optimistic (either that or they test their loads at 150 degrees F in the sun and with a 300mph tailwind), and Lyman is practically useless if you're expecting a velocity that matches the load book.  

My last use for the chrono was with 20 gauge loads I had made for target shooting with my son.  My gun has 28 inch barrel and his has 22 inch barrel. I can't remember the difference in velocity, but it was quite startling.  Something like 150fps.

I wasn't sure whether I'd get enough use out of the chrono to justify the expense, but I've changed my mind on that. It's a very useful handloading tool.  

One thing I don't do is obsess about the velocity of each shot.  I just shoot 5 of a load, check the numbers, and if they look good, I don't use the chrono again until I develop the next load.  This is probably a good thing because I have a rather appalling record of shooting my sky screens-- three to date.

[IronKnees]

     Yep! Over the years I've "nipped" a few myself..