Chrono question and I searched back 10 pages, be nice!

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LMTD

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How does it work?

I have pretty much settled on brand/model and what not however I have in my reading learned only enough to have questions!

I have read "shoot over" and "shoot through" so which is it? does the bullet go over the whole thing or through the trapazoid?

Seems to me it has to go through.


Other than the obvious answer of "how far away do you want to know" answer, how far from the firearm should it be? I was kind of under the impression about 8 feet would be ok, but perhaps the muzzle blast throws stuff farther than I thought!

I keep reading of folks shooting the device which lends me to them placing it very far away wince IMHO all of them would be a LARGE target at 20 to 30 feet. I shoot a lot and while I think I am pretty good, if I set this out at 25 yards, it would quite possibly get destroyed. I would not be overly concerned at 100 yards with a rifle, but anything over about 20, open sights with a pistol is hard for these old eyes to see.

Goal: enhance the hobby of reloading and fool with the science of it and see what happens.
 
You shoot through the uprights. I have a Chrony and it recommends 5 ft from the muzzle for a pistols-shotguns and 10ft for rifles. You should be able to center the bullet or shot through the Chrony at that range with no problems. If you don't go pretty well center it will throw the calculations off, so you want to be as close to center as possible. I don't get out a tapemeasure for the distance. I don't think it needs to be exact, just pushed back far enough for the plastic pieces that go over the top not to pop off from the muzzle blast. They still pop off everytime I shoot my 7mmSTW through it. I could use some masking tape to take care of it I guess, but it's kind of funny, so I don't worry about it. Good luck and enjoy.
 
LMTD,

Chronographs work using two highly sensitive photo arrays; same basic principle as sensors mounted on a guarge door opener to stop the door if something is in the way. Unlike the garage door sensor the chronograph uses the ambient light overhead for the light source. If you are not in bright sunlight or if the sun isn't directly over head you usually don't need the sun screens; the supports and top of the trapezoid as you called it. The purpose of the sun screens is to diffuse the light so it can see the bullet. If you do use the sun screens then you have to shoot inside the trapezoid as you called it.
 
I have tried to use the Chrony without the sun screens once or twice and I got errors, so I just used the sun screens. Thanks for helping with the terminology. You don't have to be super technical to use one, but I can't imagine reloading without a Chronograph.
 
birdbustr,

If you're at a range you won't be able to do this but if you shoot out in the desert like I do most often give this a try with your chronograph. Don't use your sun screens and shot over it. If you get and error like you did the other times you did this then set up in a different direction, if you were facing north try facing east or west. When I get and error I change directions and most the time it works unless the sun is directly overhead. If it doesn't work then of course you do have to use the screens. You'll know if it is accurate, it will be repeatable.
 
Chronographs work by use of a high speed oscillator crystal that vibrates at extremely high speed. IIRC 200,000 ticks a second. The sky screens use electric eyes that See the shadow of a bullet in flight to count the number of clicks the oscillator makes from the time the bullet crosses the first or start screen, until it crosses the second or stop screen. The number of oscillations the crystal made during the bullets flight between the start and stop screens are then converted into feet per second.

Before photo electric cells,(electric eyes), were used, chronographs used actual screens that consisted of strips of conductor that had wires hooked to them via alligator clips. The bullet broke the connection on the start screens to start the count of the oscillator, then the bullet broke the stop screen. The count was displayed by a bank of lights that were either on or off. A count was taken and converted into FPS by a chart. The bullet had to be very precisely aimed so as to not miss breaking the circuit. And you could not shoot a target at the same time, the screen was opaque, you couldn't see through it! All you got was fps, all the other fancy readings we get now had to be worked out by mathematics.

My pact chrono has to be 15 feet from a magnum rifle or it gets error readings. I haven't used the diffusers since the first time I used it 10 years ago. I don't even know where they are anymore.
 
'shooting over ' refers to shooting a bullet over the sensors' detection area...
or to just mean 'using a chronograph.'
It's like the old term' cut a check' for writing a check.Never did figure that on out.
 
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