took mine to a great gunsmith, local to my house and he drilld and tapd mine as well, BUT....
the top of the barrel is thinner than that of an 870 so he calld and askd if i wantd him to pin the barrel,
which i said yes as it is my dedicated turkey gun and its not coming apart, as for now....
just ask questions before anyone starts drilln on 1187, hope this helps, russ