If anyone is interested in a peek inside Litz' mind when it comes to analyzing accuracy and precision of chronograph's you can read here;
http://appliedballisticsllc.com/Articles/ChronographChapter.pdfI've also read his experiences with the LabRadar and I'll poke around and edit in a link if I can find it again.
With the LabRadar, which gives velocities at several user determined distances, you can calculate the actual BC for your elevation and environmental conditions. From actual bullet drops.
I use Litz's BC's to get in the ball park, they are actually pretty close.
Inherent in this statement is an assumption that your LabRadar unit is more accurate than what Litz is using. They claim 0.1% accuracy which makes for 3fps error on a 3000fps capture. Litz' Oehler was similar for precision (though I can't comment on accuracy because his 12ft Oehler was his comparison standard).
Axtell, I'm curious how you conduct your "field testing" to measure your BC's and plot out your drag curves. Is your "field testing" based on your LabRadar? Or are you using an Infinition or other doppler radar system from work? Because here's the thing; the folks at LabRadar told me the best I can hope for in capturing velocities downrange is about 150 yards with a 30 cal if I'm lucky (progressively less as the caliber shrinks). Also they told me I can't put the unit further down range like Bartholome and Litz do with the Oehler on occasion to stretch out the drag curve. They don't work like that. Does that mean you're calculating your BC's using 150yard data and extrapolating beyond to build your drag curves and get your G7 and drop values? Or are you taking drop data and backing it into your computer to give you a BC?
Help me understand as I'm simple and confused.
RCarmuglia,
It's interesting that your friend cited a SD of 8 for a 30 shot string. A long time ago, Bob Jensen who loaded the ammo for the 92 Palma matches cited a sigma 7 as the holy grail for 600 yard loads in my sport (Highpower Rifle). (I'd have to check what N was attached to that). What's interesting is he dumped powder for the 92 Palma Ammo. He shared that he got his sigma 7 through means other than granule accurate powder charging. I think he attributed testing primer lots by shooting primer powered bb's out of a special rig over a chrono to test their consistency and force (he said softer was better). Alan Warner feels otherwise on powder charges. He told me that kernel counting powder charges was the way to consistent elevations at 1K. I think he was trying to rationalize his purchase of his Prometheus. I have a Gen1 and it doesn't make me hold elevation like the Tompkins clan.
