My tactical shotgun would fit under a longish coat. Or in a big duffel. Or in a long cardboard box. Somebody carrying a long cardboard box wouldn’t be noticed in a mall.
overall length of a mossberg pistol grip is 36.375”
http://www.mossberg.com/product/shotguns-pump-action-500-special-purpose-tactical-light-forend/54129
easily consealable