Yeah but you might have left a word out in what you posted.
"Normally" A quick scan of the shotshell loadings actually
offered by the major manufacturers would have shown you
that there is much more to be had in 2 3/4" 12 ga than what
you normally see on the shelves of your local big box. Magnum
in shotshell terms refers to greater payload rather than more
velocity. Find a publication like Gun Digest that lists all loads
available in rimfire, handgun, rifle and shotshell and you will
see 2 3/4" 12 ga with up to 1 5/8 oz shot and premium buck
shot with 12 00 buck and 34 #4 buck shot. I have a box of
Winchester magnum BBs with 1 1/2" oz of buffered, copper plated BBs. Probably be pretty effective at close range but
I prefer bigger shot for large targets. 2 3/4" 12 ga has a lot
to offer if you take the time to look.