You will first need to develop a load that you plan on using or buy alot of factory ammo (try to buy it all at once and from the same place so you get the same lot #). Same goes for the handloads, once you decide what you're gonna use, buy a bunch of components so you get the same lot #.
Measure your sight height above the bore and record that.
Cronograph your loads on a day with average (for your area) temperatures and record that data. Chrono enough rounds (at least 10) to get a good reliable average. Record exact distance from chrono to muzzle. Reverse Calculate to find ACTUAL or true Muzzle Velocity.
Sight in dead on at exactly 100 yds on a day with average temp and barometer (again, average for your area). Record the conditions.
Because some cronographs are subject to error.......Personally, I would even go a little further and shoot a group or two at 300, 400, and maybe even 500 yds. Measure the drop vertically (from group center to aiming point on the target) and record all these numbers. Again, this should ideally be done on a day with the same temp and pressure as when you sighted in, or do it all on the same day when the temp is fairly stable..........Record the conditions.
You should now have enough info to send the turret builder. You will also need to tell them the altitude of where you did your shooting and the altitude of where you plan on using the gun.
One elevation turret is really only good for one set of conditions (Altitude, Temp, Barometer) and one load under those said conditions. If you're shooting 60" low at 500 yds at Sea Level and 45 degrees, you will for sure be shooting higher at 4000' and 65 degrees. They should be able to make you a turret for different altitudes (using average temp and BP) providing you've given them the above info and they have a good ballistic program to plug it all into.
There may be other things I forgot to mention. Perhaps someone else will add to this.
Verify actual value that your turrets are moving, that way you don't have a turret cut for MOA but your moving IPHY, they will tell you it's your problem when your off. Shoot drops then using an actual measurement adjust your optic to make darn sure that the value your sending them actually move your POI to the spot it should. Solid and confirmed numbers win over shooting a couple ranges then trusting a ballistics program.
High Fence, Low Fence, Stuck in the Fence, if I can Tag it and Eat it, it's Hunting!
Im not sure what you mean here. How would i go about doing this?
A couple ways to go about that: Use a ballistic program or manually calculate by using the BC of the bullet. Here's a link True muzzle velocity
I am glad BignGreen chimed in on the true amount of movement in your particular scopes adjustments. Alot of scopes don't move the point of impact exactly the amount advertised. I've seen that many many times, mostly on scopes that weren't really designed to be cranked up and down all the time. This info will need to be known. A good turret manufacturer would probably have a scope vise to check and calibrate this sort of thing, but I am only assuming that.
Just thinking out loud here but once you have all the info info needed to have a custom dial made, would you realy need it? A piece of tape over the exsisting dial marked with the drops would do the same thing or you could just tape the come-ups on the stock?
Maybe I'm missing something here?
__________________ "Make everything as simple as possible, but not simpler." -Albert Einstein (1879-1955)