If this is for a home protection firearm, a single shot certainly wouldn't be my first choice, but the pattern would be effective for that with no choke.
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A long, long time ago, a friend of mine, who shall remain nameless, walnuted the barrel of his duck hunting gun, so he cut the barrel off to 18" and went hunting, he snuck up on a puddle of ducks that were just over a dike, jumped up and flock shot them and got about 50 cripples, he and his bewildered partner(not me!) ended up chasing down ducks for the next 30 minutes or so. Needless to say, the partner never hunted with him again, if they'd been caught with all those ducks, they'd still be in jail!!
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Tim