The Chinese guns are extra hard to drill,the Chinese are sticklers for TOO MUCH Rockwell hardness than needed,case in point,Norinco 1911A1s. Milling their slides for sights can trash some lathe bits,let me tell ya. If you use a pinpoint jet of gas from an oxy/Acet torch,and turn the area to be drilled blue,it softens that area for a bit and tap to cut. An old trick from drilling/tapping surface hardened Mauser receivers...