Chrono Question

Discussion in 'Reloading' started by Blacktail, Aug 11, 2007.

  1. Blacktail

    Blacktail Well-Known Member

    May 12, 2006
    I just purchased my first chrono and have only been loading a couple months. I having some difficulty working up consistant loads with the 7 mm stw. But my question is i set it up about 10' from the muzzle. with 72.5 to 73 gr of IMR4831 and 140 TSX or Accubonds getting average of about 3180 fps. I know that should be faster just curious if the chrono is 10 ' away how much does it effect the muzzle velocity reading. This this makes any sense at all..
  2. J E Custom

    J E Custom Well-Known Member

    Jul 29, 2004

    If you have a chronograph with a proof channel it will tell
    you what your loss per/foot is ,If not I would guess at your velocity
    your only losing about 8 to 10 ft/sec.

    I had to build a blast shield for mine because the shock wave would
    cause an error in velocities on some of the big bores unless I
    moved the screens way out.

    The blast shield is nothing more than a 2x4 frame with a piece of
    plywood 1/2x3'x3' with a 3''x6'' vertical slot at the matching height
    of the screens.

    The down side is more noise.

    Placed 3 or 4 feet in front of the muzzle,this allows you to set the
    screens 5 feet from the muzzel.

    The only other reason for setting the screens close is that it gives
    you a larger window to shoot through.(Multiple targets with out
    moving the screens.

    I hope this helped