Having Trouble With Kingshead Fence

[Robin Yerloot]

Okay, so it's bugging the living daylights out of me, but every single time I throw a grenade at the Veteran pack, they come rushing up, and at least 5 of them get though the fence, sometimes I get lucky and it's just one but it's always something, I get closer to the fence, and they start hitting me and get though anyways, I'm not sure what I'm doing wrong, I did this a month ago with another pirate and it worked out fine, this is the first time it's happened to me.