When I said 'rigidly mounted scope' it was an implication that most people simply shoot a smooth bore slug gun with a bead on the barrel, or iron sights and compare it to a rifled barrel with a scope and naturally curse smoothbore barrels, kinda the way my 2 EX'S curse me.
I have not ever pinned or welded any barrel to a receiver, have not found a need for it, the worst slop I have found in a barrel mating to a receiver is a Remington 870, and if you tighten the retaining nut down enough, and do it the same every time, it eliminates it. However, I can't say for the newer 870's that don't have the barrel detent on the barrel lug, both of my 870's are older guns, vintage 1980 or earlier.
Back to a 'rigidly mounted scope'. This is a phrase I coined from a Hasting Advertisement for their rifled barrels which I pointed out in the post above. It means simply, that if you want to give a smoothbore barrel a fair shake, you need a scope properly mounted just as you would a rifled barrel. Of course, they didn't have cantilevers back in the day of the smoothbores, so I worked around that. I can tell you what we use on our guns, I know it works for us.
If I must use a saddle mount, the only one i like is the Weaver Converta Mount. Installed properly it holds zero, even removing the scope and putting it back on.
http://www.weaver-mounts.com/products/shotgunAndPistol.aspxDaughter shoots a lovely 1974 vintage Remington 1100 20 gauge with 2 barrels, smoothbore slug barrel for deer, and 28 inch barrel for birds, the gun is set up with a Weaver Converta Mount, and always holds zero wether barrels are changed or scope is removed and put back on. We've done it over and over, year after year, so we know from experience it works.
Son shoots an Ithaca 37 12 gauge(my first gun), circa 1963, gun uses 3 barrels, a smoothbore slug barrel, 28 inch modifed barrel, and a fully rifled slug barrel. Gun is equipped with a Weaver Converta Mount(they don't make it for an Ithaca anymore) for the smoothbore slug barrel scope, and the fully rifled barrel is a Hastings, with a cantilever mount. He hunts everything with that gun, swaps barrels and holds zero. The Weaver Converta Mount is a nice feature on that gun as it mounts on the left side of the receiver, so he can simply remove the top piece,(that holds the scope and rings), and slip the cantilevered rifled barrel on.
I shoot a Remington 870 12 gauge with a smooth bore barrel, that has the receiver drilled and tapped and use weaver bases and rings for a Remington 760 rifle on it. This is a 'pivot mount setup' where the scope swings away if you want to use the iron sights.
Second 870 has a fully rifled Mossberg barrel with a cantilever mount. I have to say here, Mossberg has tighter machining tolerances than Remington, the barrel is a very snug fit, with no slop at all.
I shoot 2 Winchester 1300's in 12 gauge, both have drilled and tapped receivers, one has a single rifled barrel, the other has a smoothbore slug barrel and a riifled barrel. Both have weaver style bases and rings, after all, weren't Weaver style rings the 'original' remove and return to zero rings?
Lastly, I shoot a Winchester 1300 in 20 gauge same setup as above, but with a smoothbore barrel. I'm currently looking for a fully rifled barrel for it also.
I especially like the way a 1300 barrel fits into a receiver, the 2 'splines' I guess you could call them, make for consistent and snug mounting of the barrel.
As far as smoothbore slugs, I prefer Winchesters, have tried all brands over the years, and have always had the best and most consistent performance from them, but that is obviously a generalized statement, as it depends on the indivdual barrel.
I think the best saboted slug out there is the Remington Core Lockt Bonded slug in 12 gauge from a standpoint of velocity, retained energy, and bullet performance, but as stated earlier, they are damn pricey. And again, if you're barrel doesn't find this particular slug agreeable to it, obviously, they aren't worth a nickel.
Buckskin, I did not forget about the higher velocity of the saboted slugs at all, it obviously is that higher velocity and better ballistic coefficient on saboted slugs that give them the big advantage over a foster slug way out past that one hundred yard mark. However the velocity difference is not quite as different as you stated. Reduced recoil slugs may be in the 1200 FPS vicinity, but a Winchester Foster slug in 12 gauge leaves the muzzle at 1600 FPS, and a Winchester 3 inch foster leaves the muzzle at 1760 FPS. Obviously, the foster slug sheds velocity much more quickly than a saboted slug, due to ballistic coefficient. And a 'pumpkin' is not an accurate description of a foster slug, it's a totally different design than a foster slug, being a single round ball, and illegal, at least here in NJ.
Even 2000 FPS that a Saboted slug leaves the barrel is sedate in comparison to rifle bullets from centerfire rifles, and consequently wind drift is a real issue with any slug, especially past 50 yards. I've always found it best to sight in at 50 yards then check at further distances because of wind drift. I sight in 12 gauge foster slugs 2 inches high at 50 yards and they are dead on at 100, 20 gauge, 2 1/2 inches high at 50, and they are dead on at 100(Winchester slugs in both cases, 2 3/4 inch). And as I said previously, because of poor ballistic coefficient, Foster slugs are pretty much done velocity and energy wise past 100 hundred yards, but sighted in in this manner, no holdover, etc., is required out to the maximum effective distance of the slug if you're aiming for the deers lungs, or boiler room, so to speak.
Like I said, this is what we have learned, based on our experience, hope it helps.
