G&P Front Sling Mount

[Mesaman21]

A friend of mine has bought a m203 for his G&P m4 But to fit it he needs to get the front sling mount off. Now usually there is like a split pin in my experience (mostly tm guns) but he says in this case there isnt one there is just a solid pin which he has tried to hammer out but wont come out.

now without having one in front of my i cant tell him what to do.

Anyone on here now the best and easiest way to remove it ?

Cheers