Do you shoot foster slugs through a smooth bore ?
The smooth bore in 12ga fosters is not all that accurate , I know as I own a lot of smooth bore slug guns and 100 yards is pushing it !
I have already purchase sabots ( over 150 rounds ) and want to kill a deer with only a few rounds fired , not like I'm fighting a war with my ten shot 1100 or 9 shot Mossberg 590 spraying the area cause the deer are too far out .
I want to reach out to 150+ yards !
You'd never guess that I bow hunt deer and shoot them at point blank ranges ! I don't hunt much timber during gun season like I do during archery season .

I grew up in, then, rural New Jersey; (with Peter Hathaway Capstick) and I have A LOT of experience using smoothbore 12 gauge shotguns in combination with, both, Foster and Brenneke type slugs.
AT AND BEYOND 50 YARDS THESE TYPES OF SLUGS ARE NOT ALL THAT ACCURATE; AND THIS IS ESPECIALLY TRUE WHENEVER THEY'RE USED IN A PUMP-ACTION SHOTGUN - ESPECIALLY TRUE!
Using my Remington 870 shotgun and a smoothbore (slug) barrel with rifle sights on it, typical accuracy for me at 50 (+) yards never showed less than 4 or 5 inches of dispersion; and at 100 (+) yards all I can say is, '
Fuhgeddaboudit!'
*
Because I hate inaccuracy in any long arm I've mulled over the problem of using Foster/Brenneke type shotgun slugs along with pump-action shotguns for many years, now. Here's the primary reason, 'Why' I think this combination so thoroughly stinks:
Pump action shotguns tend to have loose fore-ends; and this means that there is much more of a tendency for the muzzle to move at the moment the shotgun is fired. This is NOT a problem when using shot loads; but it is a problem when using slugs.
Have you ever noticed something that's usually called, 'lock time' in a long arm when it occurs in a shotgun? It can be a genuine damned nuisance! In the milliseconds between: (1) the hammer falling, (2) the firing pin moving forward, and (3) the slug launching and moving down the barrel: A pump-action shotgun's slide action will unlock; and the action will become unstable!
(Translation? Any inherent accuracy that's, otherwise, incumbent to a pump-action shotgun suddenly becomes significantly reduced!)
True, the pump's bolt remains closed; but the slide-action has become unhinged; and, personally, I've always thought that this is the reason, 'Why' my Remington 870 slug patterns used to open up so much.
For accuracy's sake: If I were using Brenneke type slugs (Fosters suck!) then, personally, I'd definitely want to use some sort of bolt-action style shotgun.
If - IF - you want extreme (muzzleloader type) accuracy from a shotgun then you're going to have to move up to using sabot slugs, a rifled shotgun barrel, and a bolt-action shotgun.
In my considerable experience with slugs and slug guns THIS is the only way to wring out superior (rifle like) accuracy from any slug shotgun.
* For the record, and without any false modesty, I am one of the best long-range riflemen in Pennsylvania; and there's plenty of other people, besides me, to say so.
This said: I'd be among the very first shooters to realize something is awry with a gun. If pump-action smoothbores were able to work, and work well, then I would have figured the problem out and started, 'putting them in there' many years ago; BUT, it cannot be done!
The fact is pump-action shotguns, smoothbore barrels, and Foster slugs are one of the worst accuracy-choices any marksman could make. Ideally, a gunman who needs well-placed shots shouldn't rely on this setup at any distance greater than, say, maximum pistol gunfighting range; (15 to 20 yards) and, especially, not when a target is moving.