See if a old worn thin dime will fit in the slot in the barrel( a silver one might be better, 1950 or so). If it does you have the material for your front sight. I have a RANGER made by COOEY that has an 18in. barrel with the back sight on the reciever above the chamber , that has the 1/2 moon front sight . The measurement from top of sight to top of barrel is .468mm or .1915in. The sight is .481in. long where it touches the barrel and .057in. thick ( a 1989 dime is .049in. thick but a little too big in diameter). Hope this helps.