chronographs

17 March 2002, 18:01

<burt>

chronographs

I am new to this forum but have tried to read as many previous posts as possible.
I'm interested in getting the most out of my chrono. Information on load developement, staying in safe working limits of cartridge/ gun design, and exterior ballistic information that can be gleaned from the use of a chronograph. One post I read indicated the writer did not care much about consistancy so long as it was accurate. If the velocity is inconsistant then isn't bullet trajectory different? and hence bullet impact?
Thanks for your input.
burt

[This message has been edited by burt (edited 03-17-2002).]

17 March 2002, 18:23

denton

You've got it right...Consistency of muzzle velocity is one of many factors in determining accuracy. It is an important one.

When the firing pin smacks the primer, that impact, and all that follow, send a shock wave down the barrel. Since the wave is traveling in steel, it travels at about 10X the speed of sound in air, and arrives at the muzzle well before the bullet does. By the time the bullet reaches the muzzle, the muzzle is vibrating.

Because if this, differences in muzzle velocity show up as differences in point of impact.

The whole business of adjusting primer, powder, and seating depth is an attempt to get the bullet to exit while the muzzle is moving slowly, so that differences in muzzle velocity show up as smaller differences in point of impact.

18 March 2002, 00:26

John Y Cannuck

Consistancy is a major player, but as you work through loads with your cronograph you will occasionally find inconsistant loads that are accurate. There are a lot of factors at play, and I have never read an explanation that makes sense of the phenomena.

19 March 2002, 14:31

<Dasmoofler>

Hey Burt,

First off, welcome to this forum. Be prepared to spend many hours here!

I am not an expert, but I have found that unless you're looking for a bughole, don't sweat the velocity differences too much. Of course, less variation is better, but depending on your rig, a 100 fps variation (which is alot) should not alter the point of impact too greatly at 100 yds, at least it doesn't with any loads I work with.

You will definately want to get some ballistic software. I recommend PointBlank, which is free from http://www.huntingnut.com
I like it and it's free! Sorry, I was going to try to answer your questions further, but I absolutely freezing in my basement right now!

Good Luck,
John

[This message has been edited by Dasmoofler (edited 03-19-2002).]

19 March 2002, 14:34

<Dasmoofler>

quote:
Originally posted by Dasmoofler:
Hey Burt,
First off, welcome to this forum. Be prepared to spend many hours here!
I am not an expert, but I have found that unless you're looking for a bughole, don't sweat the velocity differences too much. Of course, less variation is better, but depending on your rig, a 100 fps variation (which is alot) should not alter the point of impact too greatly at 100 yds, at least it doesn't with any loads I work with.
You will definately want to get some ballistic software. I recommend PointBlank, which is free from http://www.huntingnut.com
I like it and it's free! Sorry, I was going to try to answer your questions further, but I am absolutely freezing in my basement right now!
Good Luck,
John
P.S. The edits are only to correct my errors caused by my frozen fingers!
[This message has been edited by Dasmoofler (edited 03-19-2002).]

20 March 2002, 06:36

RogerK

In my experience, inconsitency is the hobgoblin of reloading. Incosistency in anything. That definately inlcudes velocity spread. I go looking for inconsitency when my spread is more than 20FPS. I usually find it, one time with varying weights in a box of bullets. I chrono three rounds when I start working up a new load at minumum charge then work from there. The chrono. is my number one tool.