The young soldier above is sitting in a pose common for the men in both armies, displaying his musket and wearing the accoutrements that went with it.  His hands must not have been steady when the photographer was taking the photo, thus there was some blurring which makes identifying what kind of weapon he had difficult.  Still we can see he has a single breasted frock coat, common for enlisted men in the early part of the war, along with a belt, cap box, cartridge box and probably a bayonet and scabbard obscured in the shot.