how long have you been using the sheild?
this sounds like n00b complaining.
you get the hang of where the sheild impacts if you use it enough. you time your lunge to impact the person where the impact zone is. this works when someone attempts to knife you as well. they knife, you lunge, they die.
realization that the protection zone on the sheild is very small is important. you ned to be face on to wherever the bullet's path is. your shoulders are mere milimeters from extending past the zone as well as your legs.
with practice you can attain sheild mastery.