Ever since I saw the turkey loads with the two different size shot back in the 1980's I've wondered, has anyone heard of a defensive or other shooting with that load and is it more effective than buck shot?
I've heard of a load that I believe was called "jungle buck" or something similar. IIRC it was single-aught buckshot and bb's or maybe just smaller than a bb. No clue as to whether or not it would be more effective than just buckshot but, it would seem like it would give you greater wounding potential at close range.
I confess up front that I’m not a shotgun guy, and my opinion is biased that direction. I used to carry a shotgun on duty, but switched to a carbine nine or ten years ago.
The tough part with shotguns is distance variations – a load that’s fine for using indoors at 3-5 yards can be nearly pointless at 80 yards; and a load that’s great at 80 yards can be a terrible choice indoors. If we pick the “best” heavy-projectile load for 75-80 yards, we increase the safety risks to innocents if we have to use it up close; and if we pick the “best” close-range load, we’ve really gimped ourselves regarding the potential need to shoot further out. Unless there’s a way to know ahead of time how close the threat is going to be, it’s hard to ‘optimize’ the load choice; so (like so many things) it becomes one of those times we have to come up with the best compromise, or perhaps ‘best odds’ choice.
For defensive use in a 12-gauge, imo it’s hard to come up with a better compromise than plain old 00 or 000 buckshot for most all-around uses. If it's a home-defense gun where indoors use is its primary role, I think #4 buck (#4 buck, not #4 shot) is a better choice simply for reduced-penetration reasons. But again, bear in mind that that’s strictly the opinion of someone who’s a confessed “non-shotgunner”.
FWIW, my area is pretty rural, and when I did carry the shotgun on duty, it carried 00 buck ‘tactical’ loads (hate that word; it just means “reduced recoil” in this case) in the magazine, and four 3” magnum 00 buck & two 3” magnum sabot slugs in the sidesaddle.