Firearms with gas piston assemblies have a receiver defining a passage receiving a reciprocating bolt assembly, a barrel defining a barrel axis and extending from the receiver in a forward direction and defining a barrel gas aperture, a gas block connected to the barrel and defining a piston bore in communication with the gas block bore, a piston assembly having a forward end operably engaged to the piston bore and a rear end operably engaged to the reciprocating bolt assembly, the piston assembly having a piston closely received in the piston bore and having a piston rear end, the piston assembly including an elongated intermediate rod having an intermediate rod forward end registered with the piston rear end and an intermediate rod rear end, and the piston assembly including a rear portion having a forward end registered with the intermediate rod rear end and a rear portion.