Author Topic: definition of terms (Read 424 times)

jd45 · « **on:** February 19, 2005, 10:08:29 AM »

Hello to all........can someone help me understand a couple of terms related to reloading, that bear on velocity. They are as follows:
Standard Deviation &
Extreme Spread
I think I have an idea of what extreme spread means. It's the low & high velocity numbers in a string of shots of a given load. Right?-wrong? or what? But the other-I have no idea. Thanx for your input, jd45.

Haywire Haywood · « **Reply #1 on:** February 19, 2005, 01:41:33 PM »

You're on track with the extreme spread. If you shoot a group and the low is 1000 and the high is 1100 then your extreme spread is 100.

Standard deviation is a statistical term that's supposed to describe how consistant your loads are from shot to shot....I think...

My chronograph has another number that it figures up if you have at least a 5 shot string and it's called 95% something-or-other. It's another measure of consistancy. If your 95% number is 10 then 95% of the shots you take with that load will be +-10fps of the average of the group.

Ian

earschplitinloudenboomer · « **Reply #2 on:** February 19, 2005, 09:23:57 PM »

Standard Deviation defines the velocity spread for subsequent rounds of one load. If you shoot a string of rounds which you have loaded the same, they will not all be the same velocity (even with your best reloading practices). The chrony figures the differant velocities and gives you the deviation in velocity, of that group of rounds fired, expressed as the standard deviation from one round to another in that group. The loads showing a smaller, or lower standard deviation are generally more desireable as consistancy usually improves accuracy.

Redhawk1 · « **Reply #3 on:** February 20, 2005, 02:15:01 AM »

I use to be concerned about all that also. I did not want to get as anal as my buddy and threw it all out the window. I just reload now and get the best accuracy for my particular gun. As long as I have a ball park figure from the reloading books I try not to make reloading more complicated. Now it is a lot more fun to reload. But that is what works for me, other's like to get more involved.

Haywire Haywood · « **Reply #4 on:** February 20, 2005, 05:14:28 AM »

Me neither... I just want plinking/hunting accuracy. I use my chronograph to compare what I'm getting to what the book says they got. I compare that to the pressure signs I'm getting to decide whether it's good enough or if I have some room left for improvement. The other numbers my chrono spits out are just trivia to me.

Ian

sharps4590 · « **Reply #5 on:** February 20, 2005, 03:12:05 PM »

I suppose I'm one of those geek types who wants to know everything I can ballistically, interior and exterior, about my loads. But, hey, not everyone likes to sit at their calculator and figger' up free recoil and develop their own trajectory tables for their particular load in a particular rifle.

Oh....the definition of terms you received were correct. Good shootin'!

Vic