Chronographing Loads

[Red Butler]

Howdy! 

I just bought a Chrony chronograph and I can't find conclusive info about how far I should set the unit from the gun muzzel.  I know that there has to be more distance with the larger the caliber to account for the muzzel blast effect.  I'm shooting BP and smokless for CAS.   What distance do y'all set your chronograph at?

Thanks, Red.

[Adirondack Jack]

Since we're not doing laboratory perfect work, but rather want relative readings and are looking for CONSISTENCY, the actual distance isn't that critical.

My rule of thumb used to be 12 feet for most everything, until I shot the box (oops).  Now I use an eyeballed 6 feet for pistols and 12 feet for rifles. If yer chrony-ing BP loads, set up cardboard in front of the box, and draw a "V" matching the shape of the skyscreen legs to shoot through.  That way you eliminate flaky readings caused by smoke.

Velocity won't change that much in a few feet, so consistency is most important when judging a load compared to another recipe.  In other words, just do what ya always do, and keep it more or less the same.

[Ranch 13]

 I'm partial to 15 feet, that seems to get rid of most if not all the goofy readings caused by the gases, smoke and chunks of powder etc.
I never shoot for group over a chrony , just shoot for the speed readings, that hopefully reduces the chances of a bullseye in the led. One fellar I know tapes a target to the rear guide rods so he has an aiming point above the screens.

[Sagebrush Burns]

I use the scientific measurement of three giant steps, which I figure is about 10'.  Works well for both rifle and pistol although I have never worked with black powder loads.

[August]

I set up at 15 feet.  Less distance gets the black powder to the screens at the same time as the bullet, making measurement  impossible.

[Red Butler]

To all,

Thank you very much for all of your input.  This information will be helpful for my reloading.  Red