L46 has a rolling safety-catch on the box-shaped bolt shroud;
L461 has a sliding trigger safety, completely different shroud and cocking piece, nicer shape.

They probly have different magazine/floorplate arrangement as well.

L46 introduced not long after war's end, around 1949 I believe (but .222 cartridge not introduced until ~1952?)

L461 introduced in early 1962 as far as I can determine.