This topic rears it's head every 6 weeks or so

I have not seen one of these adjustable gas plugs for the M1A. I know they exist but.... No one on this site has extensively tested one on an M1A/M14S that I'm aware of.
Contrary to my steadfast belief that Sadlak pistons are not meant for chinese cylinders due to desired diameter tolerances.... SOME chinese cylinders funstion reliably with the sadlak usgi drawing spec NM pistons.
I've witnessed it first hand and stand corrected
So, you want to use the standard 147 gr up to 174gr, as specified in the GI specs for the "real" m14.
Standard piston will suffice. For 168gr to 174 gr , regular inspection for oprod tab peening and arm straightness every 100 to 300 rounds.if tab is peened or oprod bent out of true, sytem is cycling the orod to hard.
If you want to exceed designed bullet weight threshold of 174gr, The Sadlak NM grooved piston is specifically designed and tested, in usgi/m1a cylinders to allow for use of bullet weights exceeding 180gr
This is a tested fact, in M1A and GI spec M14 rifles.
Google sadlak nm grooved piston
In reality, it takes minutes to clear your rifle, remove gas plug, remove standard piston, install grooved piston, reinstall gas plug.
No confusing the two as one has a groove