I have a gen one m&p 9mm with a thumb safety, i install a apex competition trigger and the 4.25 ported barrel kit. I bought the barrel kit used, so i don't have any of the hardware to install the red dot. My question is, does anyone know what kind of screw are used to hold down the red dot? I have some left over M3 x .5 screws and they don't fit. The thread pitch on that is too fine.