Crunchie or Nasho proof rifle. Nope, there will never be such a beast. To be honest, with the L1A1, once you were a trained soldier there was always tacit approval for the removal of handguards because the screwdriver was on the combi tool anyway. Even though the screwdriver part wasn't for that really..... Anyway, once they'd got into the gas parts and they'd sat and unclipped the gas regulator retainer, they'd notice that you could rock the gas cylinder around a bit with the explanation '......jeeees, no wonder I can't hit a cows arse with a cricket bat, the whole xxxxxxg thing is falling apart' So they'd find a suitable nail and twist the gas cyl so that it was xxxxxxg tight. Now the piston wouldn't fit into the puckered cylinder and............ Nope, I say field stripping is field stripping.
One day an Armourer somewhere in the world with a bent for humour and words and the lighter, brighter side of life will write all this down. But no one would believe that you could try to scrub the barrel out with half a shirt tail in the loop of a pullthrough. Or when it's stuck, try to shoot it out with a ballastite............ Would they John?