Chrono 1st attempt
 

Snow's gone, gardens in, wood pile is covered, and all the junk outside that was hiding under the snow is cleaned up; so time to try out the CED I got a few months back. My T bench is on the porch which is 5 foot above ground level; had to use 10 foot post for base of plate mount of V screens. So got it cut and set in, and shot a few guns. Of course I ain't the read the instructions kinda guy until I screw up and it went so so. I could only set post 12 feet from bench, not enough wire to go 20 feet. 7 mag, old factory ammo gave me an error and read 1180; that wasn't right. 6.8 with 29 grains 322 gave me 2542; sounds good. 338 fed 210 nosler partitions factory gave me 2590. Lastly I tried 480 redhawk, was like 1240. Didn't even think about the 30-378.

I figure I'll need longer wire, the shock is giving me the error. 12 feet ain't good enough I guess.

What do you all think. after reading the instructions of course?

Re: Chrono 1st attempt
 

I chrony all mine at 25 feet. the muzzle blast does effect them bad.

Re: Chrono 1st attempt
 

My Beta master Shooting Chrony has an 18' cord and I usually have it stretched as far as I can in front of the muzzle. Most of the time it works pretty good.
I don't have many big cannons...the .264WinMag is my heaviest and it throws a pretty good shockwave (about like the 7mmRemMag). Every now and then I'll get a fail when shooting that rifle with the chrony set about 15' from the muzzle.

Most of my errors though are from getting offlline with one of the sensors or just a light reflection if it's a sunny day with the sun low instead of directly overhead so the screens shield the sensors.
Your 1180 readings from the 7mm could've been caused by either the muzzleblast or stray reflections.

I saw a really neat idea for sky screens a couple weeks back that I might try someday. One guy at the range had a white plastic 10-12gal barrel with the ends cut out. He sets the chrony inside that barrel. This gives him a nice wraparound screen for the sensors that shields them from stray reflections even when the sun is at really odd angles. He doesn't have a stand for it, so it's ground-level only but I'm sure a person could rig up a stand to hold it up at bench level too.
I've draped translucent plastic grocery bags over the top of my screens before to make a larger shield area but it's kind of a rinky-dink setup compared to that barrel.

Another tip that works for funky lighting conditions is to color the bullet with a black magic marker to give better contrast against the sky/screens.