The only real differnce between the 18 and 19 series guns is the foresight mounting dovetail they are differnt widths I belive as the barrel stress releving is only just larger than the barrel diamater on an 18 sereis gun and the 19 barrels flare by quite a bit and the sight is mounted on dovetails milled into the top of the barel not the raised dovetail bolcks of the older guns.

Al