I don't know where your really coming from on this one JDe, the pressure from the cartridge is what it is, oil and hydraulics will not increase it, it will make a better temporary seal, the gas bleed on the M1A is small and late in the pressure curve, My original standard grade ( that I love and will not trade ) has the the piston nut so tight, that a 6 point socket and an air impact wrench would not remove, it shot so well, that I quit trying. So after shooting, I put solvent in the bleed hole and raise and lower the barrel and let gravity work the piston, back and forth, flush it with some brake cleaner, and then put a few drops of fp10, again raising and lowering the muzzle to make sure the piston moves freely with no help. I have had this rifle since 1991, and shot U.S. Service rifle with it, also have 8 points toward my distinguished badge with it. Never had a FTF, or bending of the OP Rod, from overpressure.
I just don't see what your describing unless you put enough lube that it got in the barrel and caused an obstruction, and that would be a lot of lube.
Turning to carbon, yes it can, but carbon buildup happens without pistons, from the unburnt gasses passing, look at a normal Direct impingement AR, Carbon happens anyway.
I look forward to more detailed explanation.