C_Yeager, and KriegHund
You are both wrong. If this was done to specification, it would work with or without live ammo, just like an M4(or other factory MG) set to full auto, or burst, will have the hammer fall when you hold the trigger to the rear and,"hand cycle", the action...This is a defining characteristic of a,"factory" full auto weapon...Even WITHOUT ammo, it WILL DROP the hammer when cycled with the trigger to the rear as the disconnector is disabled ,and the auto sear holds the hammer,"cocked", until the auto sear is forced to release the hammer by the toggle switch on return to battery, which releases the hammer AFTER,"lock up", ...Just like if you hold the trigger back on a semi auto rifle with no ammo, while,'hand cycling", the action, when you release the trigger you will hear an audible ,"pop or click", which is the sound of the disconnector releasing the hammer to the primary sear engagement(trigger face)....
Now this shoestring MG, would be a little different than a,"real" or ,"factory", MG or machined auto sear because it is external and would not work by simply," hand cylcling", the action. It looks like the actual trigger is pulled by the shoestring due to,"bolt thrust", from the return spring because the disconnector on the shoe string MG is intact and operating as normal...
Too Many Choices!?
PS-Now that I think about it, this would be a,"Select Fire Shoestring MG", becasue as I mentioned earlier, the disconnector is not disabled on the rifle, but actually woking properly, it would appear that by pulling the actual trigger even with the STMG attatched, would give you a single shot, then the audible pop of the trigger reset... Damn! Now that's what I call ingenuity, a select fire shoestring...