Thanks to everyone who responded here for your patient and thorough explanations of the shotgun details. My eyes had looked at page 204, of course, but somehow my brain managed to miss processing the section on Buckshot every single time.
I know the latter probably sounds weird, but that's a phenomenon I've noticed more than once with the T20 book: because snazzy formatting was let go to some degree, in order to cram in as much Traveller Goodness(tm) as possible into the book, sometimes useful information gets "visually buried". It can be hard to pick out specific rules information from the book (especially at the gaming table!) and the Index is a hit-and-miss affair, I find.
Or ... I'm a doofus. Pick your own adventure path, kids.
Anyway, thanks again to all who replied. I'm off to kill some flags and wreck some solar fabric now ...
LL