Setting up chrono at 40'

[SAM1980]

Trying to do some load development. I'm currently out of town working near Spartanburg sc. I using one of the local public ranges here. It's a nice facility with a 200 and 100 yard ranges. But they have berms with 40' long culvert pipes in front of benches that you shoot through. So I set my chrono on the other side of the berm. 40' from the muzzle. My guess is that this effect the readings that I'm getting to some extent, but how much of an effect is it?

 

[Sully2]

Why that far away....your wanting MUZZLE VELOCITY arent you? put them 5-10 feet in front of the muzzle

 

[SAM1980]

Did you read the post? There is a 40' concrete pipe infront of the bench. That's why it's not 10' away from the muzzle.

 

[Sully2]

Did you read the post? There is a 40' concrete pipe infront of the bench. That's why it's not 10' away from the muzzle.

Do you stick your muzzle down in the pipe? I doubt it. Place the chrono trap as far away as you can. Do ammo and rifle companys set their traps 20'-30' etc away to get readings for "muzzle velocity".

 

[Mikecr]

Past answer:
http://www.longrangehunting.com/forums/f19/true-muzzle-velocity-61081/

PM me & I'll send you a spreadsheet taking care of the math

 

[Timber338]

Try using the "Ballistic" app... it has you input the number of feet that the chronograph is in front of the muzzle and then calculates your true muzzle velocity for you.

Or, you could use any ballistic software and adjust the muzzle velocity by hand until you get your chronograph reading at 13 yards (~40 feet). the Gseven.com ballistic calculator would work, for example, where it allows you to set the range increment to any increments of yards. Just set it to 13 yards and there you go. Does that make sense?

 

[SAM1980]

Thanks for the link and the advice guys. I will try them out. I knew there was a formula to calculate true muzzle velocity, just didn't know where to find it. And no sully the end of my barrel was about a 2' away from the end of the pipe. No room for chronograph, that's why I placed it at the opposite end of pipe, but thank you for your input on the situation. Now we all know why they call it "muzzle velocity". Because the bullet comes out of the muzzle right?