MH,
Two thoughts; scope and ammo...
Scopes
Having shot 1,000yds in F-Class over the years with a Leupold 20x I can say it is possible, but not recommended. What helped was big 6ft square targets with big (44" x 44") black roundels. You can't see the individual rings through the scope but you can see them on a TV screen if using an electronic target (e.g. Kongsberg). Before the advent of TV screen shooting we used Butts parties and spotting disks, driving the string round the target based on the previous shots and wind. If you don't have this support you are going to suffer from not knowing where the hell your rounds are going. Steel splashes and splashes around the target can work but in your intended rig it's going to be like driving jelly. Your 123gn bullets are going to arrive at the target slower than a wet week, made worse by lower BC's than a larger 6.5 calibre typically uses.
60x scopes are normal for long range. 40x if it is a hot day and the mirage is killing vision. High magnification helps see what the wind is doing down at the target. Here it is either March 60x or Nightforce 55x with NF becoming more popular. March has a good reputation for repeatability. S&B 50x, Sightron's 60x and others make long range scopes. They tend to be big, expensive scopes but for long range you have to pay to play. Your 4.5-14 and 3.5-10 are just not going to cut it at long range.
Ammo
I will let someone lese chime in here. I don't use factory ammo. Obviously something accurate with a high BC to buck as much of the wind as possible on the way to the target.
Two thoughts; scope and ammo...
Scopes
Having shot 1,000yds in F-Class over the years with a Leupold 20x I can say it is possible, but not recommended. What helped was big 6ft square targets with big (44" x 44") black roundels. You can't see the individual rings through the scope but you can see them on a TV screen if using an electronic target (e.g. Kongsberg). Before the advent of TV screen shooting we used Butts parties and spotting disks, driving the string round the target based on the previous shots and wind. If you don't have this support you are going to suffer from not knowing where the hell your rounds are going. Steel splashes and splashes around the target can work but in your intended rig it's going to be like driving jelly. Your 123gn bullets are going to arrive at the target slower than a wet week, made worse by lower BC's than a larger 6.5 calibre typically uses.
60x scopes are normal for long range. 40x if it is a hot day and the mirage is killing vision. High magnification helps see what the wind is doing down at the target. Here it is either March 60x or Nightforce 55x with NF becoming more popular. March has a good reputation for repeatability. S&B 50x, Sightron's 60x and others make long range scopes. They tend to be big, expensive scopes but for long range you have to pay to play. Your 4.5-14 and 3.5-10 are just not going to cut it at long range.
Ammo
I will let someone lese chime in here. I don't use factory ammo. Obviously something accurate with a high BC to buck as much of the wind as possible on the way to the target.