On the Navy SEAL's helmet is a black Punisher coin. Possibly in reference to Chris Kyle's Cadillac Company in SEAL Team 3. Or just a oad to a classic film icon.
When the marine fires a 40 mm grenade from his rifle directly on a nearby Taliban fighter at the village, it is not supposed to explode since the fuse becomes activated only after 40 yards as to protect crews from accidental firings.
After the SEAL and corporal storm the sniper's nest, the corporal drops the rock he used to beat the Afghan to death with and it clearly floats in the puddle in which he's standing.