My spring project is to try and measure the verve and elan with which my special concoctions are exiting the muzzle. Have searched the archives and my own library and haven’t really found a discussion on the subject.
Several pictures I have seen show a chronograph firmly ensconced in a heavy timber fortification. I was thinking more along the lines of a couple of pieces of sheet metal bolted to the bar in front of the sky screens. Sooo, I thought I would come to the well of all wisdom before I start destroying expensive electronics.
Also wondering about distance from the muzzle, calibrating with factory loads etc. What would you think of doing a little dissertation on the ins and outs of your technique for chronographing shotshells, for the benefit of the great unwashed.
You mean you want me to soft soap the great unwashed? To tell the truth, I never really thought much about chrongraphing techniques. I just got a yard stick and measured three feet from the muzzle to the CENTER of my chrongraph’s screens and let ‘er rip five times, ten if I was feeling flush that week.
You can get down range velocity from the tables in Lymans reloading handbook. that’s the easy way. If you simply must, you can also chronograph down range velocities by putting a piece of 3/4″ plywood in front the chronograph with a strategically cut 2″ hole which will permit any pellets which pass through the hole to go directly over the skyscreens. Make sure to always measure with a tape measure from muzzle to the center between the two sky screens. Pacing off or guesstimating really won’t cut it in the world of aspiring Junior Technoids.
When testing for three foot muzzle velocity, I never bothered to tie my chronograph down or protect the front in any way. Muzzle blast never moved it and the LED display never got messed up with burnt powder. I guess that if you wanted to be safe, you could duct tape it to a stand or table and put a piece of clear plexiglass over the LED display on the front.
Calibrating against factory loads has its down side. If you shoot a certain factory load in matches and want your reloads to equal it exactly, then by all means test the factory load and match the reloads to it. On the other hand, never assume that factory loads of a certain dram equivalent will be dead on the nominal velocity. They seldom are. Watch out for consistency with factory shells also. 25 fps variation is not unusual. Some match quality .22 rimfire cartridges are consistent enough to set your chronograph with, but no shotshell is.
I wish that it were more involved so that I could awe the populace with my expertise, but it isn’t and I can’t. Even if it was, I couldn’t. The muezzin just calls ’em in. He doesn’t make the rules.
The Technoid at <www.ShotgunReport.com>
(Often in error, never in doubt.)