I see that you took what I mean, but sadly to say, you made the mortar into an AT weapon, for you went with the PIAT look.
The Projector, Infantry, Anti Tank (PIAT) was a British anti-tank weapon developed during the Second World War. The PIAT was designed in response to the British Army's need for a more effective hand-held infantry anti-tank weapon. It consisted of a steel tube, a trigger mechanism and firing spring, and was based on the spigot mortar system; instead of using a propellant to directly fire a round, the spring was cocked and tightened. When the trigger was pulled, it released the spring which pushed the spigot forward into the rear of the bomb. This detonated the propellant in the bomb itself, which was then thrown forward off the spigot. It possessed an effective range of approximately 100 yards (90 m).
Yes, it was an idea from a mortar, but that's not a mortar with just 90m range, the 81mm Mortar design you were after before could go from 200m-5600m range. The mortar needs the long tube for the propellant charges attached to the tail of the mortar bomb ( [link] ). The mortar works by the bomb being dropped into the tube and the firing pin at the bottom strikes the primer in the bomb's tail. When struck, the primer ignites a spit of flame which comes out many little holes along the charge shaft ( [link] ), which ignites the charges and creates an explosion. This explosion then pushes the bomb out of the tube at a high velocity.
So that's why having that cut whole right there I mention before would throw your shot off, for the constant pressure is released early.
So, like I said, what you had before was good, just needed the loading rack over the BAD (Blast Attenuator Device), not cutting in behind it.
As seen in this picture of a 81mm mortar: [link] The fat coil looking thing between the Lower Stop Band and Breach plug is known as the Cooling Fans, which help disperse the heat generated by the bomb when firing, helping keep the mortar cool.
If you have anymore questions, feel free to ask and I will answer to the best of my ability.