Magneto Speed Chronograph
I believe it was in the first episode of the new series, "Shooter," that I saw one of these on the end of Swagger's rifle. "Huh," I thought, "it's a chronograph." I kind of forgot about it after watching the episode, and then saw a report on one in a B.P.C.R. forum. It certainly was a chronograph on Swagger's rifle, and it was a Magneto Speed chronograph, and the first one I ever saw.
The report on the use of the Mag Speed in the B.P.C.R. forum gave it a very good rating, even after the fouling from a fair number of shots out of a 45/70 covered the thing. Using black powder and cast bullets, it didn't fail in its readings after all of that muzzle blast. It worked great, according to the shooter's (not Swagger's...) report. I can't help but think that the if the Magneto Speed Chrony still works fine after being coated with B.P. fouling, it probably works really great with any propellant spitting a pill out of a barrel.
The fellow shooting the 45/70 bought the "Sporter" version of the Mag Speed, which is about half the price of the offered kit shown earlier in this thread from Midway. I didn't look, but I'll bet Larry P. sells the "Sporter" version too. I just may get one.
What I really like about this chronograph is that you don't need a bench set-up with it. You can install the unit, and use it any way you need to get your readings; offhand, kneeling or prone shooting can be done anywhere with the digital read-out unit in your pocket. Seems pretty handy. Looks like it's been around for a little while, too. I'm surprised I had to watch a T.V. episode to see the thing for the first time.