I've got a late 70's vintage rig consisting of a Bushnell Banner 1.75-4.5X on a Browning BLR .308 Win and killed several deer with it between 300 and 425 yds.
Have a late 80's rig consisting of a Ruger 77 RL in 250-3000 with a Nikon 4X (fixed power) and killed a few deer with it all the way across a square 40 acre field (440 yds).
Have a 90's vintage rig consisting of a Win 70 Classic Stainless .308 Win with Leupold Vari-X III 1.75-6X and have killed deer to 600 yds with it, and several at 400 to 450 yds.

These are 1" tube scopes and the kills were all with field-expedient rests: no bipods.

Not bragging, just saying that 400 yds is reliably attainable with 4X and 600 yds is reliably attainable with 6X if you know your rifle and you know what you're doing.

Last edited by Skeezix; 03/17/24. Reason: Add info

Bring enough gun and know how to use it.

Know that it is not the knowing, nor the talking, nor the reading man, but the doing man, that at last will be found the happiest man. - Thomas Brooks (1608-1680)