R3 rear tube plug screw size…??

On the left/right of the tube? Not the ones holding the rear of the breach down or the rear screw on the trigger assembly.

One of the hex heads stripped and I don’t want to touch either any further until I find a little more info.

I MIGHT have to re-tap the plug to accept then next size up… I think I’m going to have to drill the screw out. The easy-out type stuff hasn’t even come close to budging it… I’m okay re-taping it. Those tiny freaking screws get jammed pretty good and a larger allen head will not upset me.