I bought a used camp 9 off of Gunbroker, got it yesterday and shot it today. It came with 1 Marlin magazine and it can use S&W model 59 and variant mags, 459, 659, 59 and such. So last night I was looking at the mags and they looked a lot like the XD mags. I was able to put an XD mag into the mag-well of the Marlin and it fit. The major difference is that the model 59 mags have a cutout on the front right side of the mag. The XD doesn't. The cutout is for the magazine catch inside the mag-well. So today after shooting the Marlin with it's intended magazine I put a fully loaded XD mag into the Marlin and it will hand cycle the rounds. I then placed the mag base on the shooting bench and put a bit of downward pressure on it. The Marlin will feed, fire and cycle with the XD mags. Now I'm going to contact a couple 3 gunsmiths and see if they can put a cutout on the side of the XD mag and then see if it will still feed, fire and cycle without being held against a bench. It'd be worth it to me to try this. I would love to be able to use my slightly modified XD mags in this carbine. I can buy a bunch of XD mags from Pistol Gear and have them modified, shouldn't cost much to have that done.