They should be loctited from the factory but we have seen them fly off. If you could find the nut or do like Wyn and make a nut and round it off it can be reinstalled.
I'd loctite it, I check mine periodically at the range for signs of it loosening. If it ever does I'll probably spot weld or silver solder it. Your right, no need to take it off.
In Memory of Paul "Dietrich" Stines.
Dad: Say something nice to your cousin Shirley
Dietrich: For a fat girl you sure don't sweat much.
Cue sound of Head slap.
RIP Muggsy & TMan
"If you are a warrior legally authorized to carry a weapon and you step outside without that weapon, then you become a sheep, pretending that JOCKO will not come today."