Handloads that group well at 100 or even 200 yards may not group at 300+ yards.
It’s taken me years to get my heavy barrel 700 to shoot well at 300. This is a sub 1moa at 100.
I have a go to load for several bullets that will hold 4 inches at 300 but I have to be on that day.
As far as me going to 1000. First step is to have the eyes replaced.
I have only tried 1000 yards once and I gave it up quickly. I am a good shot out to 300 without too much wind but I can’t read all the variables a bullet encounters during that 1K flight time.
"The difference between stupidity and genius is that genius has its limits" Albert Einstine