S&W M&P15 Stock Grip Removal Problem

[mwpslp]

I am trying to install a MIAD grip on my M&P15 but can't seem to figure out how to remove the stock grip. The bolt that holds it in place appears to be rounded on the inside. Not rounded off but made round rather than taking say a hex wrench. Has anyone removed their stock grip that can give me a clue? Thanks.

 

[utmaster]

I took mine off with a 3/16'' allen wrench. Be sure you don't loose the selector detent spring that comes out.

 

[mwpslp]

Thanks utmaster, got it.