How far away should you be from the chronograph when you test ammo speeds?

I should be 15 ft. from the start screen.

I use a Chrony and always place it 15 ft. from the muzzle. Never had problems even with my .270 WSM. If it's a sunny day, I use the sun shades tho.
Bear in Fairbanks

If the detector screens are mounted on the electronic instrument, then setting it too close to the muzzle (of a larger rifle) risks damaging it. The Chrony can be set only 7 to 8 feet from a .22 Hornet, but 12-15 feet is better for a .300 WBY.

With a remote set up like an Oehler 35 you can set the screens some bit closer, but the first screen needs to be beyond the "mushroom cloud" of the muzzle gasses, so at least six to seven feet is needed, which will give you an "instumental" distance of eight to ten feet.

The closer to the muzzle the less adjustment you have to do for true muzzle velocity and the wider the "shooting window" if your are shooting groups simultaneously. However, if you start to get screwy readings then you need to move the screens further away.

Hey bear, I'm waiting on that CED to come in on mail plane and it warm up some of course. How far for my 30-378; she really barks with 99 grains of RL22. Is 15 feet enough?

The best check of Muzzle blast effects is to shoot at both 15 and 20 ft. If there is a difference that's the answer.

Never measured exactly. Past 10-15 years I've used a Master-Beta Chrony so I just seat it as far away as the wire from the display will allow.

quote:

Originally posted by Zhurh:
Hey bear, I'm waiting on that CED to come in on mail plane and it warm up some of course. How far for my 30-378; she really barks with 99 grains of RL22. Is 15 feet enough?

Though mine is a Prochrono I set it out 15 feet when shooting my 338-378 Wby with or without the muzzle brake. The loads I use for that are 104+ grains of IMR7828 for 225 grain bullets and 118+ grains of US869 for 265 grain bullets. The readings seem consistent with either of them.

Ken....

quote:

Originally posted by Zhurh:
Hey bear, I'm waiting on that CED to come in on mail plane and it warm up some of course. How far for my 30-378; she really barks with 99 grains of RL22. Is 15 feet enough?

Zhurh:
To be honest, I duuno specifically about that kinda loudenboomer but..
Think I'd try 15 feet first and if that doesn't work try 20. Since HEAT doesn't have a problem with his .338-378, I'd gues you'd be ok with 15 ft. Good luck, lemme know how things work out. Still too cold to hit the range here - windy & about -5 deg. or so.
Later, Bear in Fairbanks

...and don't forget if you're a cast bullet shooter and you have the chronographs what you should over the whole device, protect your screen from gas checks that may come off the bullets. They do have enough energy that close to wreck your machines LCD screen.

If you like the set or screens close and your rifle has a large long muzzle flash, you can shield the device with a big piece of cardboard or plywood with a hole for the bullet to pass and it will stop most the muzzle flash.

Zhurh--I set mine at 12' with my 30-378's and 338-378 and have had no problem with reading on the chronograph. I am shooting 100-101gr of RL22 with various 180gr bullets out of my 30-378's.

The listed velocity measurements on factory ammo are taken at 3 feet from the muzzle. I have very few problems taking readings at that distance with the chrony secured to something stable and an angled deflector shield(plexi)protecting the base. This has worked on .30-06 down through shotguns. My experience is you need to play with height over sensors and with or without screens. I will admit to having an odd situation or two where it will not work, black powder especially.

I've been using "sky screens" since '75 and have found you can get erronious readings, especially with lower velocity loads, if the start screen is close than 10'. I prefer 15'. The muzzle blast can sometimes trigger the start screen before the bullet gets there with lower velocity loads as the exit velocity of the gas is a lot faster than the bullet.

What ever distance you use just be consistent from set up to set up.

Larry Gibson

Thanks to all of you guys for info on Chrono. I heard the mail plane fly over, expecting the CED to show up any day now; now if she warms up some; was minus 18 last night; ready for winter to get on it's way.

I try to set everything up pretty much the same every time to make the readings as consistant as possible.

I've taken the remote cable and marked it off at 12' & 15'; although I've never had to use the 15' measure. Lay a sand bag on the bench with the end of the cable under it where the remote will be placed and pull the cable taught. That's where I place center of the Tripod. Not real exact but at least the "same" every time.

I also hang a sandbag under the tripod leg supports to keep those pesty breezes from blowing things over.

The correct distance is what the manual that came w/ your chrony states is proper.

I have a 10' cord attached to my Oehler 35P and it works very well. 30-06 is the biggest gun tested however.

My first screen spacing has been 10' for about 15 years with a 4' screen spacing with my Oehler 35P and I have never had a problem..shot everything from 22LR to 50BMG and shotgun.

I use about 20 ft