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Chronographing shotgun loads

6147 Views 5 Replies 5 Participants Last post by  unclenick
I shot through a chronograph with my shotgun a couple of days ago and read a startling number on one shell. I wonder how accurate these rigs are with a fragmenting mass passing through them. Anyone know about this?
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I have been reloading shotshells since way before I was old enough to legally buy components. What I have found is that you have to do the chronographing when the sun is just right but without using skyscreens. I use both a Shooting Chrony and a Pact set up back to back so that I can verify the velocities. I set the first one up so that the muzzle is exactly 5 feet from the first reader on the chronograph, the two readers are 2 feet apart, so since the velocity number generated is the average between the two readers, the velocity measured by the first chrono is my 6 foot (2 yard) velocity. The second chrono I just look at to verify that the first chrono gave a good number.
The way I protect the front of my chronograph (yes the muzzle blast still hits pretty hard at 5 feet away) is to take a 25 round box of lead shot ammo and turn all the shells in it so that the brass is on one side, then I place the box directly in front of the chrono with the crimp end facing my shots on the small table that I built to use as a stand for front chrono, the second chrono is on a tripod, and is lowered so that the readers are about an inch lower than those on the front chrono, so it's pretty well protected too.
I don't think these chronos will reliably pick up the shadow of individual shot pellets from most sizes, but I know they will pick up a single BB from a BB gun, but anything less than 2 shot is questionable. So shooting at closer range is necessary since you are most likely to read the speed of your shotcup, and at a couple yards, it's still going pretty close to the velocity of the shot pellets, after about 3 yards, the difference grows pretty rapidly.
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