M-1 Carbine Piston

[dfariswheel]

Before removing the piston nut I strongly suggest cleaning up as much of that ham-handed staking as possible.
That much could cause stripping the threads in the gas piston.

This is a case where you have to be cautious because you don't know what was done.
It could be an altered nut, piston, or even gas cylinder.
This because even though the nut can't be moved, it's still functioning.

 

[Patrick L]

Everyone realize the pictures posted are NOT the OPs. That is a responder posting pics for illustrative purposes. So we are not looking at pictures of the carbine in question.

My piston moves freely with finger pressure. My castle nut was lightly staked, in fact I routinely disassemble mine once or twice a year for a thorough cleaning. I do shoot cast bullets out of my carbine, but it's all carbon I clean off, no different from jacketed ammo. I scrape piston carefully, and brush out the housing on the barrel.

 

[Matt_X]

On the following webpage is a cutaway view of the piston assembly on the barrel, and photos of the nut and piston disassembled, as well as factroy staking.
The U.S. Caliber .30 Carbines - Barrel Manufacturers

 

[Retired W4]

On the following webpage is a cutaway view of the piston assembly on the barrel, and photos of the nut and piston disassembled, as well as factroy staking.
The U.S. Caliber .30 Carbines - Barrel Manufacturers

Matt, that link to The Carbine Collectors Club has an incredible amount of information. I saved it so I can refer to it any time.

My plan now is to take it to the range to fire a couple mags full of clean, modern ammo, with the hope of burning out whatever is keeping the piston stuck forward when the bolt and slide is in battery. Although it's likely not related I will get a head space gauge to check on that as well.