lrb111 wrote:iirc, the best way to open that pattern is with a rifled slug barrel. Otherwise, it's going to be pretty tight at normal self defense distances. My Mossy/Maverick 88 is identical to those patterns.
The problem with rifled barrels and shot is that the amount of spin imparted to small projectiles is negligible: the pellets don't stay in contact with the walls of the barrel the whole way down the barrel; they don't receive axis-centered rotational spin like a slug. The net result is that the pattern tends to form a ring and expand, or widen, as it travels. For defensive purposes, you want a pattern that pretty much fills up its impact diameter with a uniform cluster of holes. The expanding ring of shot fired from a rifled barrel means that as the distance to target increases, you're more likely to miss the intended point of impact area completely and hit around it.
Too, the rifling causes some amount of deformation of the pellets. And while I've never done (or seen; hm, I wonder if Box-o-Truth is watching) a side-by-side patterning comparison and effectiveness testing of identical shotguns, one with a plain cylinder choke and one with a rifled barrel, my assumption would be that the pellet deformation would decrease the effective defensive range.
I know that's what happens if you choke down on 00 to try to get a tighter pattern. Birdshot can squeeze through the choke, but big pellets don't fit as nicely, and they get mashed together and against the choke. The result is misshapen pellets that won't shoot true and can cause dangerous flyers, pellets that zing off in unexpected directions. The misshapen pellets
do decrease the effective range.
But the relatively tight patterns txinvetigator showed on his targets are just about what you want--and would expect--from a defensive shotgun, IMHO. You don't want a two-foot wide spread at seven yards. You want all the pellets to hit the intended target (at pretty much the same time), and you don't want pellets flying past the target.
With 00, the effective range for a defensive shotgun with an 18"-20" barrel is about 25 meters, give or take. That's one reason I keep some slugs on a side-saddle; anything over about 80 feet--and I have time--I'm ammo swapping. With #4 shot, the effective range is less: about 15 meters. The pattern spread with 00 should average somewhere around 2.5" for every 10 feet traveled...give or take a significant margin for error because of type of shot, barrel length, etc. That's why txinvestigator recommended patterning a particular shotgun at varying distances using defensive ammo.
While I'm rambling, one last thing I had drilled into me is:
Anytime you pick up a shotgun for personal defense, you should be carrying a sidearm, too. The biggest downside to a shotgun--especially in stucture clearing--is that it isn't very retainable. That's one reason mine all have slings. If you have to do some really tight corner clearing, you're better off getting the shotgun out of the way and using a pistol. Use the right tool for the job at hand. And the best method of stoppage reduction for a shotgun in a fight is to pull it close to your body with your off-hand, and go to your pistol with the other hand.