Open Trigger? I think thats Like you have to have a Trigger gaurd. I don think ive ever seen a gun with out it.
Velocity Lock-Down Device:its the thingy to change the velcoity on the rear of your gun i guess it has to lock
Velocity lock-down is a fastening mechanism so that you cannot adjust your velocity during the game. Older guns did not have trigger guards until they were required for standard safety. You should have no reason to use a product that does not have one, except nostalgia.