The rubberized Master Lock trigger lock will not budge, if secured correctly. Weapon loaded, or otherwise.
I have *personally* popped off a locked rubber-shrouded Master-branded trigger lock off a Hi-Power using a single Craftsman blade screwdriver. Not recommended, as I'd knocked a small spot of the finish off of the trigger guard. (That pistol was unloaded, FWIW.)
BTW i took one my real cheap trigger locks off. I stuck a flat screw driver into it and could not unlock it. (i was not trying to break it just turn it, to unlock, I also didnlt use a really small flat head, just the one i had sitting on bench)