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Prone with a Chrony

 
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Old 05-17-2012, 07:27 PM
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Prone with a Chrony

First time out with a chrony shooting prone. Besides not shooting the chrony, any words of advice on the best method to set up?
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Old 05-17-2012, 07:54 PM
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Re: Prone with a Chrony

A couple bricks and a 2x6 and keep it 18 feet away from the muzzle so the blast does not shake the screens. Turn your scope to the lowest power so you can align your shot between the rods to get adjusted then turn it back up once you see you are not going to shoot the chrony. I had 3 of the shooting chrony's in line on a longer 2x6 once. They all had different readings by about 40 fps.

Jeff
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Old 05-17-2012, 08:17 PM
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Re: Prone with a Chrony

My chrony dont have any "screens"..???
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Old 05-17-2012, 08:49 PM
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Re: Prone with a Chrony

Jeff: Thanks, bricks and sticks I can find. Interesting info about variance in your 3 readings. Is that a kind way of telling me to not put too much faith in the results? I downloaded and would like to use the new AB app to figure velocity but 1) I have not figured all that out and 2) I do not have data from as far out as what the instructions indicate I will need. Enojoyed your post about stepping out the back door and testing at 900...that would be nice!
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Old 05-17-2012, 09:27 PM
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Re: Prone with a Chrony

Yes that is exactly why you can't put a lot into the velocity reading from one chrony. I have 2 of the same make and they read around 40fps different. I shot prone a couple weeks ago with the chrony just sitting on top of my rifle case placed 10 feet in front of the muzzle. This worked fine but I like Jeffs idea about moving it back a bit. Lots of little rocks blasting away at it can't be good though mine showed no signs of damage. An EZ-UP shade over the chrony keeps the lighting consistent and another over yourself is nice too!
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Old 05-17-2012, 09:46 PM
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Re: Prone with a Chrony

Boom, just use your chrony to get an average MV. Then put that in the AB program. Next check your zero to make sure you are on. Then shoot some 3 shot groups at 500, 700 900 and 1000. Keep a log of fiels conditions like Baro , temp ect. Also log how low or high the groups were and at what distance. Once you have that you can fine tune the AB app with changing the MV to get the dial ups spot on with your rifle and the app.

Jeff
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Old 05-17-2012, 11:46 PM
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Re: Prone with a Chrony

Jeff, at what point in trying to make everything match up on the calculator do you start using more than one bc? Is there a distance you add a second and then at further distance you add another or is it just an option when you can't get things lined up perfectly?

I tested a box of factory ammo the other day at 800yds. First I zeroed at 100 and then did an actual drop test at 800. I had an aiming point 16 feet above the target and aimed for it with the scope still dialed for 100. I then dialed in the correct elevation and shot for the center of the target. It was a min low for some reason so I dialed up and fired 3 more groups. They all were about 10" with 2 flyers. Without the flyers they were more like 4". The winds were not playing nice going from 8 all the way around to 3 at 3mph-8mph. I used a kestrel and entered all the environmental parameters into my Bulletflight app. I entered the heading in and had spin drift and corriollis accounted for. The groups were both left and right but vertically within 4" of center.

My question is in what I did to make the calculator match up perfectly. I used a chrony and have shot these over the chrony before so I have a fair idea on a true velocity. I used the calculate bc feature on the app and was surprised to find the bc reading .347 instead of the advertised .441??? It does match up perfectly however to the actual shooting. I played with velocity a little but it never got exact. Should I worry about not trusting the calculated bc or just run with it? Would using multiple bc's help in this case?

Sorry to the OP for highjacking but thought it might benefit others who read this.

Thanks, Jason
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