The load is a howitzer from WWII, Korea, maybe early Viet Nam. The current towed unit is an M777, google it and see what it looks like. Also, google towed artillery, us army and see what the current towed units look like. That said, it could be a 155mm howitzer or an 8" howitzer. For a 155mm Long Tom, you need a longer barrel. Check on the dates, I do not think they would have been on a BN flat, unless going to scrap.