This is a temporary measure and shell tracer effects are going to be reintroduced with the upcoming v.0.6.5 update, which is to go live in the end of June – beginning of July.
http://game.worldoftanks.com/news/n...re-tracer-hacks
好像是為了避免有些人把它修改得相當明顯而近乎於作弊，所以暫時取消彈道效果，之後的更新會再恢復或改良?