http://www.garandgear.com/m1-garand-ammunition
I highly recommend using one of these unless you plan on sticking to handloads. My Dad and I use them and both our Garands still pass the "tilt" test after many hundreds of commercial 150gr. rounds down the tube. Use care when installing, though, as they are made from quite soft steel and will strip if overtightened. Better to replace the plug, though, than the gas cylinder, lol!
Use one of those "Ported Gas Screws" when shooting anything but M2 ball.
They are great.
The trick to screw torque, which has apparently been lost to the modern man, like making fire w/o a "Bic" or communicating w/o a cell phone...
...is Grease.
Even on the CMP board you will read, "clean the gas cylinder lock screw and install dry, and then torque the crap out of it so it won't come loose"... because theirs is always coming loose, and yours will too. (because you will clean the gas cylinder lock screw and install it dry, and then torque the crap out of it)
Screws hold - because the threads flex a little when properly torqued.
If the threads are dry - friction builds up as the torque increases - not thread deflection.
Vibration - will rattle the un-deflected threads apart and the screw will back out.
Grease - reduces friction to nearly zero, so the torque goes into thread deflection.
Grease - also acts as a film thickness dampener, and very light adhesive, to negate vibration between the threads.
Grease - protects the threads from seizing due to corrosion.
Clean - Grease - Torque - wait (for the grease to displace and film) - re-torque.
This goes for sight/scope mounts, rings, and cap screws as well.
Never had Any screw/bolt come loose on its own.
GR