Originally Posted by cowboy
My comment on don't count on your chronograph being 100% reliable was based on a lot of trigger time compared to the average individual plus the fact that an engineering degree taught me that not everything functions as it was intended 100% of the time. After burning up more barrels than I like to admit chaseing the one hole zero with single digit SD/ES I have developed the opinion that I will use my chronographs constantly but will never overide field testing even if my SD/ES says double digits.
The 280AI that I am using now showed an ES of 40 and a SD of 15 the last time I checked it on the chronograph with 168VLD's. That same load has been a little lower and a little higher at times past. With that said field testing at 6- 8 and 1000 showed vertical spread much less than the chronograph would have led me to believe. Bottom line is I don't feel the chronograph has the final say in what I'm going to shoot. The chronograph is a VERY valuable tool but it doesn't get final say.
I don't claim my chronographs read 100% accurate velocity, or operate 100% reliably. I don't claim I can know the recorded velocity is accurate to within +/- 10 fps or even +/- 20 fps. But no one has identified any other affordable technology better able to establish the MV of my loads, or their loads. There is no better tool available. What better option is there?
You stated you owned two chronographs, but not whether you shoot over the two simultaneously in order to establish their reliability and credibility. I own two, and I run them in tandem as described in the ES/SD thread. Es/sd
By doing so I do claim to be able to identify any significant hiccups in reported velocity, and to be able to ID accurate ES and SD, because ES & SD are difference-based calculations, and my dual chronograph method establishes the credibility of the relative difference in velocity when the delta of the difference in velocities is low for all shots included in my ES/SD data set and determinations. For that reason I discard a load with unacceptably high ES/SD based entirely on my chronograph data - if the load is intended for long range hunting. Even if it one-holes-em at 100 yds. I know they'll string vertically at long range, because I know the variance in muzzle velocity must be expressed in vertical stringing at extended range. Disregarding the high ES simply means I need to work a bit more until I find a different load with lower ES that also shoots well out of the rifle.
I'd always heard the 280 AI was an easy-to-load for cartridge, and expected to have an easier time getting the ES/SD down to lower numbers than I'm getting. I'm struggling to improve upon ES in the 25-30 range and SD in the 10-13 range. The numbers are tolerable, but not what I'd hoped for. H1000 is the most consistent powder thus far, having tested H1000, Retumbo, and RL17. I'm not finished yet, but closer to the end than the beginning of load development with the 168 VLDs. I may try one box of 180 VLDs and see if there's any significant improvement. My barrel is 9 twist so stabilization with the 180s should be fine.
I don't long range hunt in the severe temperature and snow conditions that you describe, and have experienced. Hunting my style in Alaska under those conditions leads to a wilderness survival experience or worse, rather than an enjoyable hunting experience. No roads, no horses, no cell phone communication, no help. I haven't joined the ranks of hunters carrying Satellite phones up here, in spite of the the obvious health & safety benefits. For the temperature conditions I do hunt in, I pre-print drop charts for three separate elevation/atmospheric pressure conditions including angled/sloped shots of 0, 10, 20, and 30 degrees, as well as a column for a 10 mph cross wind. Those charts are packed along with the pocket PC/ballistic software program. I use these charts for back-up confirmation that the predicted dope from the ballistics software hasn't been botched by bad input/operator error. And for back-up should the pocket PC fail. The dope off the chart is generally very close. If it's more than two clicks off, I'll rerun the PC program again for confirmation prior to prepping for the shot.
I won't go out of my way to compete with you in this thread. That wasn't and isn't my interest. My background is graduate engineer, practicing and professionally registered in the State of Alaska. Been shooting and hunting with rifles for the past 41 years, the last 32 in Alaska. Doesn't mean I'm special, better or worse, or anything of that sort. Simply posted here for purposes of supplying my background & experiences.