Post by: Crunchy on August 15, 2013, 11:52:23 AM
Post by: thinkingman on August 15, 2013, 02:15:02 PM
What should I do with chronograph data. Do you average all rounds and use that as your standard, then use that data for trajectory info?If you're calculating ballistics, then yes.
I look for the spread (deviation) to see how well I'm loading.
Post by: Crunchy on August 15, 2013, 10:00:06 PM
Post by: norsepeak on August 15, 2013, 10:16:32 PM
Post by: jay.sharkbait on August 15, 2013, 10:23:24 PM
Is a spread around 50 acceptable?
How far away was the target? And did you see any vertical stringing?
Post by: bearpaw on August 15, 2013, 10:47:04 PM
Is a spread around 50 acceptable?
I think that sounds high too.
Post by: HUNT on August 15, 2013, 11:06:02 PM
Post by: argie1891 on August 16, 2013, 12:51:28 AM
The spread may depend on how accurate your chronograph is also. Some are better than others.
I will second the above my chrony is not anywhere as good as a pact I recently picked up. I hardly every got low extreme spread with it same loads on the pact are much better. I think the reason is the distance from the front and back electronic eye and a bigger window to shoot through. argie1891
Post by: HUNT on August 16, 2013, 06:21:30 AM
Most accurate chronograph I have used, hands down.
Post by: BULLBLASTER on August 16, 2013, 08:13:18 AM
Fwiw when I chronoed my load for my 300 rum out of 10 shots I had a standard deviation of 9. That's better than I was expecting.
Post by: jay.sharkbait on August 16, 2013, 09:55:38 AM
If you have a known distance and a fairly accurate BC you can get much better numbers using predictive algorithms.
Post by: BULLBLASTER on August 16, 2013, 10:44:08 AM
I'm just throwing this out here, but you really don't need a chronograph any more.How will you know if the bc is accurate without knowing the velocity? Also how will you know how consistent your load is? Velocity is a very important part of load development and data for long range shooting.
If you have a known distance and a fairly accurate BC you can get much better numbers using predictive algorithms.
Post by: jay.sharkbait on August 16, 2013, 11:12:58 AM
I'm just throwing this out here, but you really don't need a chronograph any more.How will you know if the bc is accurate without knowing the velocity? Also how will you know how consistent your load is? Velocity is a very important part of load development and data for long range shooting.
If you have a known distance and a fairly accurate BC you can get much better numbers using predictive algorithms.
The algorithm is key.
It's like celestial navigation. It doesn't tell you where you are. It tells you how far away you are from a designated point.
Post by: Feanix on August 16, 2013, 02:57:37 PM
Post by: jay.sharkbait on August 16, 2013, 03:43:14 PM
Ballistics Coefficient is a product of velocity
BC is a product of mass, diameter , surface area and surface condition.
Post by: dontgetcrabs on August 16, 2013, 04:33:24 PM
Ballistics Coefficient is a product of velocity
BC is a product of mass, diameter , surface area and surface condition.
Why does BC go down as velocity slows?
Post by: Bob33 on August 16, 2013, 04:39:41 PM
Post by: Feanix on August 16, 2013, 05:28:53 PM
Surface area and surface condition do not equate to drag coefficient. Drag coefficient is a product of velocity. Most bullet manufacturers use standardized drag models when calculating their stated BC and most are averages. I think only Sierra lists different BC's for different velocities, and not on all bullets.Ballistics Coefficient is a product of velocityBC is a product of mass, diameter , surface area and surface condition.
Getting off track.
Crunchy: I use chrono data as a check for consistency in my loads (ES AND SD) and use the average velocity as a starting point for trajectory. A standard deviation of 50 is pretty high. Make sure you charges and seating depth (measured from the ogive) are consistent. When i was tuning the load for my 308 i kept getting fairly large SD's and ended up changing primers.
Post by: argie1891 on August 17, 2013, 01:05:24 AM