DIY Simple Pipe Fitting Zip Gun Built Legally

Most zip guns are illegal because they #1, do not have rifling and #2 are not the basic shape a gun.

without rifling, that classifies as a smooth bore, aka shotgun which requires an 18" barrel.

being disguised or in some other shape than a gun, is an AOW, class 3.

this has a Redman rifled liner and a grip perpendicular to the bore. good to go !