Marines field new rifle optic for better accuracy, hit probability February 23 Chief Warrant Officer 4 Dave Tomlinson, infantry weapons officer at Marine Corps Systems Command, demonstrates the Squad Common Optic attached to the M27 Infantry Automatic Rifle. The SCO is an improved optic that improves target acquisition and probability of hit with infantry assault rifles. They began fielding the system in 2021. (Matt Gonzales/Marine Corps) The Marine Corps recently began fielding a new rifle optic to improve shooter accuracy at distances with both the M4 carbine and M27 Infantry Automatic Rifle. The squad common optic is a magnified day optic that has both an illuminated and nonilluminated aim point that’s built to increase effective target acquisition and probability of hit, according to a press release from Marine Corps Systems Command.