Just standing there, shooting straight at the enemy hasn't worked since the 1800s (or at least the last Die Hard). Cover is king when it comes to gun fights, and these 12 periscope rifles from our friends at Oobject let you shoot without giving your opponent anything to shoot at.
Demonstration Of A Periscope Springfield Rifle
Corner Peeking Rifle Periscope Patent
Springfield Periscope Rifle
Note the chain of triggers.
US WWI Periscope Rifle
Allows shooting over a trench.
The Vanderlip Pocket Bayonet Periscope
Chandler Trench Periscope SMLE Rifle Adaptation
William Beech And His Invention, The Periscope Rifle
Periscope Gun Based On A US M1903 Rifle
Note how here the stock itself is hinged making the gun fold out into a periscope.
Array Of Periscope Rifles From The Springfield Armory
Belgian Periscope Rifle
M.95 Loopgraafgeweer Dutch Trench Gun