SBR or AOW???

i have a loose understanding of class 3, not an interest of mine.

what is the "rules" for buying a short barreled shotgun?

tax stamp? would you be on a "list" and have to open your home to atf visits?

i saw a pretty good deal on a 1187 police, but it has 14" barrel. if it is a big hassle i'll pass.

also:

ak47 pistol + front grip is AOW?

i think i read that a "class7 ?" can add a front grip and log it , then sell to individual for $5!
is that true, whoe here is a 7?

thanks for any info.