Going from 165 to 168 - drop chart help

Discussion in 'The Basics, Starting Out' started by tlk, Feb 9, 2011.

  1. tlk

    tlk Well-Known Member

    Apr 11, 2008
    I am changing from a 165 SGK to a 168 SMK in my 30-06. I have already done a 400 yd ladder test and the rifle shows to be liking a load that is only .2 gr higher than my SGK in H4350. Which is good - everything is a real go in the loaded round department. But here is the deal: I would like to know the FASTEST and most ACCURATE way to get the scope dialed in for this new load. Would it be best to re-zero at 100 yds and shoot in increments out to 900 yds, noting the drops in inches and make a drop/come-up chart from that or what? Ideally, I would like to have the data I need to make a drop chart in a day and with a minimal amount of shots - less than say 50 if possible. Then come back a second day and confirm scope clicks, etc. I want to get the data - accurately - as quickly as possible so I can using my powder and range time for steel , etc. How would you go about doing this? Thanks for the help.
  2. Joaquin B

    Joaquin B Well-Known Member

    Sep 10, 2009

    I don't know if you have access to a long distance range, but I did the following, using the 500 meter rifle silhouette range in Tucson:

    1) Recorded the load's muzzle velocity, the temperature that day and the range's elevation, while zeroing the rifle at 200 meters on paper (needed 3 rounds).
    2) Used the 300 meter gong to determine and record elevation settings (dialed up 3 MOA to start, needed 3 rounds - 2 to adjust, 1 to confirm).
    3)Same with the 385 meter (dialed up to 6 MOA to start, Needed 3 rounds), and 500 meter gongs (dialed up to 9 MOA to start and needed another 3 rounds).

    Once I had my 200, 300, 385 and 500 meter settings, I set paper targets using the shoot-n-see type to get a view of the bullet impacts and repeated the process at 250 (started with 1 MOA), 350 (started at 4.5 MOA), 400 (started at 6 MOA) and 450 (started at 8 MOA) meters. This will be a lot easier if you have a portable gong...which I am now planning to build.

    I then toyed around with JBM Ballistics (internet freebie), setting the distances in meters and at 50 meter increments from 0 to 1000, then inputed different muzzle velocities until the software produced MOA adjustments which were very close very close to what I observed the various distances I shot at.

    I realized that the trajectories calculated by software differed somewhat to those determined by actual shooting, so I only use them as a reference.

    I will be now be using the adjustments recommended as starting points by the software program at distances beyond 500 meters, once I have my portable gong made. I use meters because, having been shooting silhouette for so long, I am used to measuring everything in meters.
    Last edited: Feb 16, 2011