Ah yes, crooked guns. Highly inaccurate and with drastically reduced ballistic performance. Unfortunately in Infinity terms it wouldn't be very OP because a solution to the problem was developed during WW2 (high calibre weapons carried by infantry squads) which means you'd spot the periscope gun making the attack and then shoot the wall roughly 50-80cm from the muzzle. Most walls won't stop the bullets and some bullets (I'd imagine DA rounds from a Multi Sniper) will be hitting with enough force to turn the wall into a direct template weapon. Still, something a bit less crude might be possible, such as a gun that shoots tiny missiles - essentially smart bullets from Who Framed Roger Rabit... possibly a lot smarter than those come think of it - capable of Speculative Fire without Impact Templates.