The short-stroke piston in the M1, M2 carbines are in a housing that is stacked to the gas chamber which is an integral part of the barrel. Probably the worst accessory ever sold at gun shows was the piston-nut wrench for these weapons. These tools were not issued to the individual soldier, who was forbidden, in the American services, to disassemble the pistol nut from the weapon; they were for the use of trained articifers. That nut needs to be staked in. Loosing of the nut produces gas blowby, probably among other things, and causes malfunctioning in these weapons.
I have heard of no totally effective way to thoroughly clean out the corrosive salts from the the piston, piston nut, and the gas expansion chamber that is part of the barrel. If that part of the barrel is badly rusted, the barrel becomes unserviceable.
I have never understood why any country would make this caliber of ammunition with a corrosive primer when the United States had perfected a non-corrosive primer of high quality for carbine rounds at the first production of the cartridge in the early 1940s, or whenever (don’t feel like looking up the dates right now).
It doesn’t matter a bit how long a weapon is to remain in service - if it is in the hand’s of soldier in combat for one year, one month, one week, or even one day, and it doesn’t orperate properly, for whatever cause, in my view, as an ex-enlisted man armed with an M2 Caribne for 18 months of my serivce (albeit in peacetime), than a real crime has been committed by higher authority above that soldier.