Some simple math here. The l/p raketa/strela in Memory LOD work for aircrafts (depending on vehicle's simulation) only. Proxy of CfgNonAIVehicles available is maverickweapon (maverick of A10 and hellfire of AH64 are using this design), which work for land vehicles, but unfortunately it has fixed direction same as the Vehicle but not the turret (by the way, this is same for l/p raketa/strela). However by directly calculation it's able to design such a function. In this way what the editor has to assign is not selections in Memory LOD of model but formula in scripts of vehicle's Fired-EH.   The invariant things is the relative position among launching positions and the turret. Variable is both the 3D direction of vehicle and turret. Let's start our analysis here. The "VectorUp" of vehicle is a vector parallel to the axis of turret (osaVeze), and the direction vector of turret mostly can be regarded as the direction of the projectile (shotBullet, shotShell, shotRocket with nonzero thrustTime and shotMissile within initTme will have a invariant direction), which can be obtained by "VectorDir". These 2 vectors admit an unique direction perpendicular to both of them (obtain it by vector cross), notate it as "vectorH", meaning relative horizontal direction, and then obtain "vectorV" (relative vertical direction) via vectorH and projectile's (turret's) direction. Having know "vectorH" and "vectorV", the script can assign the initial position of projectile by current ammunition. It's seems faster to use setPosASL than setPos according to https://community.bistudio.com/wiki/Code_Optimisation .   A video of TOS-1 unit (model is from DKMM mod).   Another one of tunguska unit (model is from DKMM mod as well). Its cannon is noticeable. Here is the script for M270 MLRS unit (one can find this model in M29064mm.pbo, or in COC mod, or in latest RCWC 4.9).   This design requiring 2.01 ArmA:Resistance for commandsVectorUp and VectorDir. In 1.96/1.99 it'll cost more pre-calculation due to lacking of script commands. The "VectorUp" can be obtained by 3 sensors. 3 points admits a plane, and the "UP" vector can be calculated by these sensors (the "camCreate" is recommended for it's effect is local in network game). As for the projectile's direction, it's velocity vector can be used instead. Besides, 1.96 have to use setPosbut not setPosASL commands.