Harpoon tips in 688i

So I have been having some issues with the harpoons in the game. About 1 out of three actually hit the target. Most of the time the just fly right by even though I have taken the time set the seeker and destruct range. They fly right at the target and right when you would expect the report that it has hit, it just flys right by. I am having a horrible hit/miss ratio on using this weapon and have almost decide to not use them, even though I know they are required in later missions. Any and all help would be appreciated! Thanks