I was under the mistaken impression that the "fins" on the Foster-type slug were there to impart spin. I got corrected on here over last season, and I went back and looked it up. Sure enough, the fins are there to reduce the bearing surface thereby reducing drag, and it also gives the slug some room to deform a little if it hits a tight choke.
I'm not sure about the assertion that you must use sabboted rounds out of a rifled barrel. All I know for sure is that most slugs nowadays are marked with "for rifled barrels only" or some such thing if the manufacturer thinks its not a good idea. Whether or not they'll be accurate is another question. Sabots add a whole level of complexity to the physics of the shot, and you are already talking about a lot of variability -- not only model-to-model and load-to-load, but individual shotgun variations and even variations in one batch of ammo to the next. With slugs especially, I would prescribe a thorough review of the manufacturer's website and read everything they have to say about a particular slug.
've read MShunters post on slug barrels and sights...
This is a serious ? I and need to explain reason for it bare with me..
I've been shooting my 20ga browning for 30+ years...It's like a 26'"(or 28 ?..I'd have to look) long smooth bore modified choke..so just pick a 3'' shell..be it bird or slug and shoot...raised vent bead site...Now I can with confidence shoot a deer 100yrs and be dead on...that said
What...other than a shortened barrel ...is the advantage of a "slug" barrel for a shot gun?...I know they are rifled...ps never shot a shotgun with a rifled barrel..reason for ? I suppose..
The answer to this question is that a slug barrel is usually has the following features:
1) a Cylinder or Improved Cylinder choke-- slugs do not need to be choked.
2) Either rifle sights or the facility to attach a scope-- some folks get better results with this over a bead or a rib
3) Shorter barrel-- it allows you to mount and swing faster.
If you can shoot a deer with a 26" vent rib modified choke barrel at 100 yards, there is nothing to be gained from switching barrels. You've got a winning combination. Do not touch a thing. You might want to put some glue-on rifle sights on the vent rib, but if you're confident with the current sighting method there is nothing to say you'll derive and great benefit from changing. 100 yards is about as good as it gets out of a conventional shotgun.