all the plug threads look to have been protruding into the combustion chambers past the threads in the head. the first few threads look to be covered in carbon to corroborate that too.
i'd get shorter reach plugs (shorter thread wise). the plug tips shouldn't get anywhere the pistons..... ever. too long a plug seems to me the only way they can do that.
neil.
RN14YC plugs are correct for a 2 barrel 273. If there is something smashing the ground electrode, there is an issue in the cylinder and not a plug length problem. Messing with plug length screws with heat ranges which can cause other issues.