I'm no expert on mortars, I've only seen them being fired on videos on youtube, but every video I saw there, and everytime I've used the mortar in Arma2, never has the barrel recoiled this much.

The barrel will nearly always bounce up and down for about a second or two after being fired. This is totally unrealistic due to the fact the barrel on the mortar will move maybe a mil or two after being fired, not bouncing up and down wildly like you may get when a rifle or AR is fired.