Jagger couldn't be traced back to him. So why not just get rid of it? Hell, why not just leave it at the crime scene, he had gloves on. Don't mobsters often drop the gun and leave it there after they shoot someone? No prints and can't be connected to him.....leave it there. Bringing it home makes absolutely zero sense. Another case of dumbing people down in order to facilitate some part of the SL.
Also, Jagger was going to the Quartermaines to arrest Sonny. He told nobody? Sonny called Jagger and said he'd confess to everything and Jagger insisted it be at the Quartermaines......are they not checking his phone? Also, apparently Jagger was unarmed? Wtf?