The total mounting space (length of the 1" tube) measures 5.3".
If your Remington 788 has a picatinny scope base and a sporter profile barrel, I recommend using the high 1" diameter Leupold Rings at the link below to mount the Leupold VX-3HD 4.5-14x50mm Rifle Scope.
https://www.opticsplanet.com/leupold-prw2-riflescope-rings.html?_iv_tube-diameter=1-in&_iv_ring-height=high
The Leupold VX-3HD 4.5-14x50mm Rifle Scope could potentially be used to shoot at very extended distances but there are a lot of other factors that come into play when shooting that far. Here are some guides that may help you in your selection of a scope and give some information on long range shooting.
https://www.opticsplanet.com/howto/how-to-choose-a-riflescope.html
https://www.opticsplanet.com/howto/how-to-start-long-range-shooting-on-a-budget.html
The Leupold VX-3HD 4.5-14x50mm Rifle Scope is a Second Focal Plane scope meaning that the reticle will stay the same size as magnification increases. In a First Focal Plane scope as magnification increases so does the size of the reticle.