Can you kill a dude with birdshot from a 12ga? You sure can. Most of the cops I know can tell at least one story of some bad guy laying in a spreading puddle, having had a rathole chewed through his middle by a close-range blast from a low-brass #7.5 target load.
But when I say "close range", I'm talking three to ten feet from the muzzle. Which is damned near gun-grab distance in a long-gun fight.
These shots were from less than twenty feet. Birdshot is for birds.
The distance at which birdshot turns from an instantly-lethal .72" Glaser Safety Slug to an ugly and enraging flesh wound is closer than you think it is and is less than the longest possible shot in your home unless you live in a refrigerator box. You can also miss with a shotgun in that distance. Put a sight on that splattergun and learn to use it.
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