You don't dial to shoot a 300 yard deer you hold for trajectory and wind , remembering its the horizontal distance , contour effect etc
Go zero your 243 at 200 yards and go test the true trajectory of your load 50 yard intervals up to 300 and the value of a fixed full value 10 mph wind , halve it , quarter it heck double it based on a wind and angle basis.
This is how it's done real world , real time
Big difference between shooting tactial type matches and hunting real animals where one shot no sighter are where its at
Good idea to practice on crows or something to learn your personal limits without that sighting shot that most matches allow 2
Have a look at PRS shooting, no sighters and have to shoot a steel target from an improvised shooting position at varying ranges depending on stage etc, with a time limit which puts pressure on, similar to how you may feel with a deer in the scope.
I can safely say that by practicing at these matches I am a more confident marksman while stalking, both positionally and from a dialing perspective.
While at a range day a few weeks ago it was very well highlighted that most people didn't have a clue how much to hold over when pushed to even 200M (let alone 300), whereas those of us dialling (all with no sighter) that have done these 'tactical competitions' that you seem so scorning about were hitting the bull...
I am by no means saying you cannot achieve the same result holding over, merely most cannot.
With regards to the OPs original question, I would recommend getting some sort of ballistic Calculator on your phone (Strelok, Applied Ballistics, Hornady 4DOF etc) then input basic data that you know, such as muzzle velocity, sight height, bullet data (BC, make and model if it is on the app etc) and this will give you a good starting point, you should be able to input the distance, an estimation or measurement of windage and get an approximate solution for your first trip to the range. From there in most apps I have seen you can tune the data output once you are there, this is most often done by putting in a known distance you have shot and the drop you applied to hit the target. This will make the drop curve the app is referencing off closer to the true drop you will see. There are many rabbit holes to go down with this sort of thing, however I would say get stuck in, have a play and see what you get!
Hope that helps somewhat?
Ben
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