Maybe the MK IV setting on the MK V isn't that accurate...

[HBob]

Not really a fan of Lamb of God, but they apparently had switched from MK IVs to MK Vs and did a video for Mesa demoing their new amps. Now there's a new Rig Rundown video fro Premier Guitar (great series on Youtube) showing they are using their MK IVs on tour.

 

[Rhoads]

I see Lamb of god a few time from the time that they said it was using Mark V but let me tell you,
i have seen their rack. They have a Mark V (Sometime, Willie Adler dont have one) but there's always a Mark IV on there rackmount, Always !!! I think they use Mark V ,but it was more for the sponsoring because Mesa don't do the Mark IV anymore. They still on the ads of the magazines with that.

 

[HBob]

In the most recent video of their rigs they never mentioned any MK Vs. At all. I thought they might just because of the endorsement stuff. Each of the guitarists has two IVs. One of the guys is now running a MK IV and a Royal Atlantic at the same time. I'm thinkin' that would sound freakin' huge.