They've been making stubby loads for 12 gauge for a few years that I know of. These are 12 gauge shells that are about an inch long. They are great for closer in work and still pack enough wallup to be handy for homestyle self defense. I'd reckon a handful of those aren't too much more inconvenient than an equivalent in 7.62 x 39, except for maybe packaging. There too, it wouldn't be too awful to have a speedloader tube with 15 of those stubbys in it to jack into the magazine of my pump gun, assuming they don't jam up the shell feeder when cycling.

Also referred to as 12 gauge kurtz ammo.

With decent sights on a good shotgun with the proper ammo, 150 yards is fairly doable, 200 yards would be pushing it, but then I seldom take shots beyond that range for anything other than target practice. 90% of all the critters I ever killed were taken inside of 50 yards anyways, even with my big 338 win mag and my 7mm mag. 100 yards is a pretty realistic limit for ballistic projectiles out of a shotgun in any case.

If it works, it works. If it don't, more probably wasn't going to do much better.
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)