OK. Suppose you have developed a drop chart for a load and it does not work out on the target, ie zero at 100 yd, yet a minute lower at 500 than the drop chart calls for. How do you modify the drop chart to make it correct?

Can you make the adjustment on the chart manually?

seeing that the ballistic coefficient is probably not the problem, I would assume the MV is wrong. Go into a ballistics program and drop the velocity until it matches the drop at 500 yards. Tehn reproduce your drop chart.

The two main factors to manipulate are velocity and inches per minute in your sight.

You can move the chart around quite bit by playing with the velocity, but do you have any reason to believe your chronograph is wrong? Any particular reason to believe its right? These things can be checked, rechecked, and cross checked.The quick and dirty is to simply shoot at 500 yards with your 100 yard setting and physically measure the drop in inches then convert that to MOA.(Divide inches by 1.045 then divide that by the range in hundreds which is 5 in your case.) Either it matches the chart or it doesn't. The target is always right.

Then there's your scope (or sight). Test it at 100 yards, takeing one shot then cranking a whole turn into the elevation then takeing another. Do it again with another turn, then star over and repeat 3 or four times. You will either have 3 nice little groups or one heck of a mess. If its a mess you can stop right there and replace the scope. If its showing 3 little tight groupsthen measure the distance between group centers and divide that number by the amount of minutes in a turret rotation. The result is the number that has to go into your program in the inches per MOA slot and it doesn't matter if the scope says bushnel or Nightforce on it.

Programs are only as good as the numbers that go into them.

Or you could sight in at 500 and slip your scale until your POI, chart and turret are in agreement. The 1 MOA error will be at 100 instead of 500 but may be easier to manage there.

Thanks for the comments, Gentlemen. I just figured out what number I had to multiply my 500 yd drop by to make it come out correctly and then multiplied the other drops by the same number. And yes, dog, the target is always right! BTW, I am from western Montana and have a farm at Midale, Saskatchewan.

the other variable not mentioned in your post is the ambient conditions vs your drop chart. I'm sure as you know density altitude (temp, humidity, and pressures) plus head winds or tail winds can make a big difference in vertical path of a bullet I've had as much as 7 moa at 1000 yards from one day to the next.....

quote:

BTW, I am from western Montana and have a farm at Midale, Saskatchewan.

Midale 'eh? Dug a pile of oil wells down that way awhile back.