January 20, 2003, 12:56 AM
Decided to pick up a chrony and play with it some. I am interested in the way folks go about developing loads using chrony data; any thoughts/replies/tricks/tips appreciated.
January 20, 2003, 02:19 AM
I use mine every chance I get, to check velocity averages, and velocity extreme spreads.
As most people here will tell you, low velocity spreads don't always equate to good accuracy, but can indicate possible problems.
For instance, I reloaded a wide range of Unique powder loads using Oregon Trail 250gr LRNFP bullets, Starline brass, and WLP primers, for my 45 Colt Blackhawk (5.5" stainless).
I found that Unique is so darn consistent, that I might as well have saved my time, and loaded only the minimum load (6.5gr@740fps), and the maximum load (10gr@1051fps), and plotted a straight line between! All the loads in between fell right on a linear slope for the respective charges. :D
Also found that 24gr of H110 with the same bullets, cases, and primers doesn't burn worth a crap! Average vel was as low as 1100fps, with vel spreads well over 110fps! :(
Switched to CCI350 large pistol magnum primers, and the average jumped to 1350fps, while the spread dropped as low as 36fps. That's the kind of stuff you usually can't see without a chrono. Mag primers were absolutely necessary for this load in my gun.
OK, so accuracy is another story, and I find that chrono measurements, and shooting groups for accuracy at the same time, is too distracting for me. If I want to try a particular load, I run a few over the chrono to be sure the velocity is acceptable, then move to a bench rest without the chrono in the way, and check for accuracy. Sometimes I even do this in separate range visits.
Also, don't expect the chrono to work perfectly every time, as they are really sensitive to light conditions. Too little light, or even too much light (direct sun) will often cause problems. Patchy bright clouds are also troublesome, as they can create multiple bullet shadows over the sensors, and give you some spectacular velocity readings! :D
Another problem is the muzzle blast/shock waves from heavy loads. These can trigger the start gate before the bullet ever gets there, and cause readings as low as two or three hundred feet per second. :rolleyes: :D
Moving the sensors farther from the muzzle will cure that problem.
My chrono (Pact Pro) works just as well (if not better) without the diffusers, so I don't use them anymore, unless I want to extend the shooting session a little past normal daylight limits.
Have fun with your new toy! They open up a whole new window into reloading statistics. :)
January 20, 2003, 05:24 PM
I use my chrony to identify accurate velocity "windows" in which given bullets perform well in given barrels. I also use it to identify if competition reloads are sufficiently powerful enough. It also helps me see how consistent my powder throwing is, by identifying extreme spread and standard deviations in my loads.
January 20, 2003, 06:01 PM
I built a box for my Chrony and it is covered with clear tape re-enforced typing paper to prevent shadows. I use a auto headlight, hooked up to the car battery, when there isn't enough light. It sets on top of the box. I also have a 3/8" baffle plate to protect the Chrony from muzzle blast and stray particles. Been using it like that for over ten years.
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