I thought i had heard just about everything in my time but this certainly tops all.
A playing card,edge on at 50 metres!,less than half a millimetre thick!.It can't even be seen at that range.
Now come on,tell us it was placed edge on, on top of a block about 150mm square to give an aiming point first,so you know more or less where it is,and then you would hit it eventually after enough shots,maybe.
This kind of talk just encourages irresponsible shooting by the more impressionable amongst us.