So will 40S&W fit and work well in 9mm mags? They look similar in size. Reason being: A friend gave my some 9mm HP mags I wondered if they could fit and feed the 40 of my father in laws. Good day for me today as my Father-in-law just bought me a Kel-Tec PLR16! though I bought his daughter a 1966 Mustang last month when I could have bought the Kel-Tec peice. BIG GRINS!