Hi Josh,
It will probably depend on whether the M16 is a metal or ABS model.
I've a full metal MGC M16A1 which has a completely blocked barrel. I also have MGC XM177 and M4A1 models in ABS and HWABS respectively. Both these have vented chambers that will allow smoke to pass through the barrel.
The barrels vent straight through but have the usual flat metal bar running along the length to ensure no projectiles can pass through.
Marushin use a different gas-bypass chamber that allows smoke to vent through the barrel but there is no clear, straight pathway from chamber to muzzle making it absolutely imposible for projectiles to travel through.
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Cerwyn
Hobby collector of Replica model guns and Militaria.
also member of Living History Reenactment Groups.