Yes, the Beretta 9mm 18rd magazines will work in the Chiappa M9 Stoyan.

according to the chiappa site yes they will work "Based on the current U.S. Army service Pistol, Chiappa Firearms' M9 series updates this modern classic with ergonomic finger grooves and a superior slide mounted safety/de-cocker. Comes standard with two 15 round magazines (compatible with Beretta 92)" chiappafirearms.com/f.php?id=36

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Hi Stoyan, Yes I spoke with Chiappa and these will work on the chiappa m9 9mm. Hope this helps.

according to the chiappa site yes they will work "Based on the current U.S. Army service Pistol, Chiappa Firearms' M9 series updates this modern classic with ergonomic finger grooves and a superior slide mounted safety/de-cocker. Comes standard with two 15 round magazines (compatible with Beretta 92)" chiappafirearms.com/f.php?id=36