These Turkish shotguns that use AR12 or MKA 1919 magazines have slight differences in magazine dimension. This is largely caused by machining and quality control among the gun maker and the magazine maker. This is why when you use different brands of magazines, some can be incredibly tight fit. I would take a look at the magazine that you are having a hard time removing and see where it is if there's any scratch to it (that's likely the spot where it is getting stuck) and see if you could sand it down or something like that. If not, I would look at a factory magazine made by the same manufacturer as your gun. I hope this helps!

Well, these two gents have given you the necessary info already. Good luck!!

Dave, unfortunately this happens from time to time. Normally with extended use it will work it's self loose. So you could either try working the magazine and eventually it will loosen up. You could also find the contact points, where the finish is starting to come off and polish those area's and add light grease/lube afterwards. Either one of those should do the trick. Hope this helps and you're very welcome.