Hello from a fellow varmint shooter.
Back before we had rangefinders that would go beyond 400 yds, we would go out ahead of time and stake off distances in 100yd intervals.
This was for prarie dogs in eastern Wyoming. Some of the guys got into the VHA 1000 and 1500 clubs doing this.
My furthest rimfire kill was really close to 250 yds. 22 magnum, pretty close to 20 years ago.
Sure is fun, glad to hear you had a great time. Surely is addictive.