Great as a singer, though he was in a few good movies. Many of his movies were losers, including the Matt Helm duds. Coincidentally, the author of the Matt Helm books did some gunwriting in later years. I recall two of his articles in GUN DIGEST, perhaps thirty years ago.
Donald Hamilton was the only outdoor/gun writer I know of who made the transition to writing bestselling novels.
He also wrote a Western or two and mysteries other than the Helm series.
A skilled sailor/yachtsman, he knew what he wrote about when he had Matt in boats. I think he wrote a column for a yachting title and he returned in late life to his native Sweden and restored fancy boats.
He didn't name gun models much in his books, but any S&W enthusiast will spot the exact models with no problem. His usually issued carry piece in the early books was a M-38 Bodyguard, which he didn't like, for inaccuracy and heavy recoil with warm loads. As a sort of OSS man in WWII, he preferred a Colt Woodsman .22 and owned one, which appeared in, "Death of a Citizen". Other .22's were described in late books, for specialized assassination use. In and after, "The Betrayers", he had a S&W M-60 stainless snub. In one book, impersonating another man, he carried a snub Colt Python.
Rifle data and knife stuff was also pretty good.
I liked Matt Helm almost as much as I did James Bond and Modesty Blaise. Peter O'Donnell's Modesty books were probably the best. He was the sole British writer to do an exceptional job with guns, BTW. And the knives with which he armed Willie Garvin were also well thought out .
BTW, I read an article in T V Guide or somewhere that said that Dean Martin liked to shoot at coyotes with a K-38. He owned a ranch somewhere that he could do that. His Rat Pack pal Sammy Davis, Jr. also liked guns and was quite a fast draw artist. This is uncommon in Hollyweird and merits mention, although long past.
I found Dean Martin to be a good actor and singer and didn't really detest him. I did NOT like Jerry Lewis and was glad when their partnership dissolved. Although I did not see Martin as a valid Matt Helm, I enjoyed the films for what they were. I'm just upset that most who learned about the character did so from those campy movies. Ditto for the James Bond films after, "Thunderball."