[fastarget]

We went to chronograph loads yesterday using a prochrono and holding the muzzle 6 feet from it. We had one of the club members come over and ask if he could use it.
After he chronoed his 28ga load from 3 feet, he told us we should be adding 15fps to our numbers for every foot we are standing from the chronograph.

How do you calculate your numbers?

 

[JACK]

Kinda the opposite as the shot pod accelerates a few pellets in front. And gives you a false faster reading. Stay with the ProChrono instructions. My Prochono numbers were virtually the same as the official wad tester guys. I used the 6' length

 

[fastarget]

Thanks Jack,
That is what we have always used 6', and we have in the past used production ammo for reference. The gent had me thinking that it is a lot of velocity to add on to the chrono numbers.

 

[AveragEd]

ProChrono once told me to deduct 35fps from my readings as only the leading pellet is clocked. Very much more costly units will clock the mass but as stated, they are salty!

Ed

 

[Sky Buster]

ProChrono once told me to deduct 35fps from my readings as only the leading pellet is clocked. Very much more costly units will clock the mass but as stated, they are salty!

Ed

My Pro Chrono manual states to add 3% to the velocity reading for shotshells. Ohler (probably
the best chrono you can buy) says to use 3 feet from the first screen and to use an open
choke, Skeet ot IC

 

[fastarget]

To add 3% may make sense, since there is a slight drop in velocity from the muzzle until the load reaches the chrono after the pressure behind it dissipates, 30 plus fps(still that seems like a big number). From 3 feet I would assume the chronograph is seeing one large bullet probably.