FWIW when I transferred to Aberdeen Proving Ground, MD and got into the weapons and ammunition test business several things were learned about trajectory and programs.
Firing Tables are published for MGs etc and these are not calculated on computer programs because the BRL (Ballistics Research Lab) concluded down range performance duplicates computer projections 5% of the time. It was found that programs would be right on at say 300 and 700 yards and high or low at 200, 400, 500, 600, 800, 900, 1000 yards.
If anyone would like to know how we did it I will post it but it is a fairly long procedure I will be glad to share.
In the interim I will tell you how I do it with my personal hunting rifles.
You have probably noticed politicians are now using plastic signage to get their name/pictures out and after the election many of them do both to go around the state and pick up their signs.
I have been involved with local Republican Party here for many years and we are asked to go around and remove the signs and T posts they use to erect them. The material of choice is known as Coreplast and comes in 4X8 sheets. It used to sell for like 8.00 a sheet to the printers who screen print them for politicians.
I have a 600 yard range behind my place and when the party Chairman put out the word to take them down I was right on it quick. Another shooting friend and I would leave out in my F250 and cover the county and when I got home had a stack of 4X8 signs about a foot thick and T posts.
Some of them are only printed single side so I build frames 48" square, cut them in half and set them up at different yard lines 100, 200, 300, and 600 yards.
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For hunting rifles I mount a 4X8 Coreplast on a 2x4 frame 4X8 and cover it with news print. You can go by your local newspaper and get end rolls off their presses for a couple bucks.
I have rifle zeroed for the range I want. For instance I zero at 300 yards normally for POA/POI (point of aim/ point of impact. I put a 50 yard pistol target at the top of the 4X8 target standing up and go back to 400 yards and fire 3 shots.
Then to 500 yards and shoot 3 and then to 600 yards and shoot three shots.
I then go down and measure the drops from the center of the target down to each of the 3 shot groups, record them and determine the average drops for each range.
Generally on 308 and 30.06 if you are zeroed at 300 you will be 12" low at 400 which you can estimate. For closer shots you shoot at 100 and 200 yards and record those. You will find your HOLD UNDERS at 100 will be about 5" and at 200 around 4".
I like the Burris Ballistic Plex Scopes and I zero the top cross hairs for 300, then I start moving back till I find where the next hash mark zeros mark the spot record that, then move back more till the next hash mark zeros and mark that and continue on till the bottom thick post zeros, mark that. I then go back with a 300' tape and record the ranges.
Now you can use the scope to give you a educated guess at the range. I take a piece of 6" PVC pipe cut 24" long and find the point where the lower points touch the bottom of the pipe and the top of the pipe and mark that and record that distance.
As your range increases the accuracy of range determination becomes more critical. Hope this helps you guys that have missed at the longer ranges.