Using the Hawke BRC software

I am trying to set up the BRC software for my Hawke 6-24X56 SideWinder SR12 that I have on my Condor. I have the gun set to shoot JSB 18.1 pellets at 900 FPS.

The BRC software wants me to calculate the ID, what ever that is, by compairing the muzzle velocity against a speed taken down range. I can get the muzzle velocity, using my Combro, I am not going to try shooting thru the Combro’s 1/2″ diameter sensor rings at 35 or 50 yards. LOL.

If anyone else is using the BRC software, and the JSB 18.1’s, what did you set your ID at?

Does anyone know what the velocity difference would be, again using the JSB 18.1 pellets, betweem muzzle and 30 or 50 yards? I think that the starting velocity would not make a difference as long as the muzzle and downrange FPS were taken in the same shot string.

Thanks
oldgoat