Steve,
The longest range for my use is 200 yds unless the corn fields are picked
My first run when doing the test I shoot here at home where I have 130 yards that is pretty well protected by trees that cut down most of the wind drift and I just shoot a two shot string. This also gives me a positive sight picture at a small aiming point to keep the errors down.
The groups are a little smaller than they would be at 200 but the result is the same, just smaller at 130 yds.
When I get the best worked out I move to the 200 and shoot a 10 shot for a better average and fine tune the load.
I found shooting test loads at extended distances there are to many variables caused by aiming errors or condition changes.
A good 200 yard load I find will hold to the extended range unless I cause the error shooting. I see this when between shooting the final test here at home and going to the gong or long range shoots. If it shoots well here at home it performs well at the shoots.