i found out the problem
i always instinctively get my artilery or tank to fire the first shot at the middle of the enemy
anyway, then what was happening were the next shots even though i was pointing the cursor at tracks or turret, were still auto firing at the middle of the armour and doing nothing!
ive corrected that, by instead of hurridly firing at enemy armour without armour, i know pick my spot beforehand and go for the side or the turret thing
ps also for artilery i find the smaller guns far more effective than the larger guns
and also katushas even though they can wipe out a ton of enemy, also use up so much resources