I have fired a 'confiscated' 12 ga. H&R Topper that was abbreviated to a barrel length of about 9 inches with the stock sawn off to approximate a pistol grip. Ergonomics? Ergo what?
It was an absolute SOB to shoot, somewhere between getting a full-power swat to an outstretched, palm out hand by a tennis racket and hitting your fingers with a hammer. Two handed, with the weak side holding down the barrel with the web tended to negate the sting a little...very little.
Muzzle flip is such that it makes one glad it only has one round since a follow-up shot could hit the operator.
It patterned approximately the width of a boxcar in the length of a boxcar. Muzzle flash is pretty impressive if you're into Hollywood boomers, but thereagain, it'd start a fire.
Myself, I'd rather look at a Serbu Super Shorty than the Auto-Burglar; at least you have more to grab onto and 3 in the tube.
If you're that hot for something like that, then the 'Witness Protection" Remington 870 might be the best choice of all.
Regards,
Rabbit.