Retrieverman, just because you have never had the right comination
to shoot sabots or shooting the right ones and spending alot of time
at the range testing and doing research, don't speak for everyone else.

I have hada 200yd range on my property since 1967 and do all the
testing and research with smooth bore and rifled bore guns. Have
tried just about every combo and every ammo out there.

I shoot a BRN A-5 with a Hastings Paradox barrel with a Simmons shotgun
scope. I can put everyone in a 6" pie plate @ 75-80yds using Win. BRI sabots.
You say that is not acceptable to you, well all the vitals on a deer are in a 8"
circle. I have the recovered expanded sabots on the shelf for display. Some
expanded to 60-65 and 70 caliber.


Sabot slugs
These days most of the major shotshell manufacturers also offer sabot slug loads for 12 and 20 gauge shotguns. These are for use only in fully rifled barrels. How a long arm with a fully rifled barrel can be termed a "shotgun," I fail to understand, but that is beside the point. These loads are essentially equivalent to the kind of loads used in modern, high performance muzzleloading rifles.
Since the Remington catalog is still open in front of me, I will use their sabot slugs as representative of the type. Bear in mind that, as with sabot bullets for muzzleloaders, they're plenty of variations available.
Remington offers 12 and 20 gauge Premier sabot loads with both JHP bonded lead core bullets and solid copper hollow point bullets. The former are called "Premier Core-Lokt Ultra," and latter are "Premier Copper Solid."
The 12 gauge Core-Lokt Ultra sabot bullet is a .50 caliber, 385 grain HP semi-spitzer. The catalog MV is 1900 fps and the 100 yard velocity is 1648 fps. The ME is given as 3086 ft. lbs. and the remaining energy at 100 yards is 2325 ft. lbs. The trajectory of that load looks like this: +1.8" at 50 yards, +2.4" at 100 yards, and +/- 0" at 150 yards.
The 20 gauge sabot bullet weighs 260 grains. It also has a MV of 1900 fps, and its velocity at 100 yards is given as 1615 fps. The ME is 2084 ft. lbs., and the remaining energy at 100 yards is 1506 ft. lbs. The trajectory of that load looks like this: +2.0" at 50 yards, +2.7" at 100 yards, and +/- 0" at 150 yards.
As I wrote at the outset, this are similar to the ballistics obtainable with high performance, .50 caliber, inline muzzleloading rifles. Accuracy is apparently not quite as good as the best muzzleloaders, as Remington claims consistent 2 1/2" 5-shot groups at 100 yards. But that is impressive accuracy from any kind of shotgun--even if it is really a rifle!
Clearly, the use of these sabot bullet loads completely negates the rationale behind the "shotgun only" deer hunts. Not only are these shotguns with rifled barrels technically rifles, they shoot like rifles. In fact, they equal traditional big game rifle cartridges such as the .45-70 and .38-55.
For example, a .45-70 rifle shooting a 400 grain bullet (BC .214) at a MV of 1900 fps has a trajectory that looks like this: +2.1" at 50 yards, +2.8" at 100 yards, +/- 0" at 150 yards, and -7.2" at 200 yards (Speer figures). That is a very similar trajectory to the Remington Core-Lokt Ultra loads described above.
The Hornady .45 caliber, 300 grain XTP-Mag sabot bullet used in their 12 gauge factory load has a BC of .200, which I suspect is not much different than the BC of the Remington sabot bullet. Holding a scope's horizontal crosswire level with a buck's back should put the bullet into the heart/lung area at 200 yards.