There is a way to lock your FPS on either the menu and in-game.
go to: Documents\My Games\UnrealEngine3\ShooterGame\Config\ShooterEngine
In this folder you can find these commands:
[Engine.Eninge] (This is I think made for the menu of Dirty Bomb)
bSmoothFrameRate=FALSE
MinSmoothedFrameRate= Value
MaxSmoothedFrameRate= Value
[UnrealEd.EditorEngine] (This is I think made for Dirty Bomb In-Game)
Make them:
bSmoothFrameRate=TRUE
MinSmoothedFrameRate= 5/22
MaxSmoothedFrameRate=make this the max FPS you want.
Hope you guys understand this, else feel free to respond and I’ll help you out.