Below is a diagram of two identical .177 pellets, both fired horrizontally with no barrel flip etc. one having the usual zero yaw trajectory the other having just 1.5 degrees of initial yaw in the vertical direction. The tracks are just what you would see if you stood alongside the trajectory and could see the pellets flying along. The barrel is pointing along the horrizontal zero height line. The real pellet is still starting out flying horrizontally but the yaw is creating aerodynamic lift. Probably the first thing which will strike you is that the maximum height is very small which is true but it still represents some degree of pellet lift above the barrel line. Of course many will say that is just theory and nothing like that ever happens in real life but in real life no pellet ever leaves a barrel without some yaw or yawing rate on it. Also if the modelling is so wrong please don't tell the army, or navy of just about any country as they all use it for aiming their guns and training their personnel.