How did you try to release the slide?
If the empty magazine was in the gun, pulling back on its slide only makes the slide-lock dig in deeper. The follower of the empty magazine actuates the slide lock.
The only way to release the slide of a 1911, when it has an empty magazine in it, is to press the slide-lock lever down against the upward force of the magazine spring.

The only correct way to release the slide of a 1911 is to first remove the empty magazine.
Having first done that, then you can either press the slide-lock lever down, or you can "slingshot" the slide.

I am shocked—shocked—to learn that a gunshop salesperson didn't know that very elementary step.
It is true with many more guns than just the 1911.

yes, that's very unusual that the gunshop didn't know better.
Must be a very small gunshop, usually there are a few other employees on hand.

Thanks for the info..I have a Beretta PX4, and a Ruger SR9C, and both of the slides will release with an empty mag in them. This is my first 1911...I guess maybe they're just a different animal...Again, many thanks.

Originally Posted by moondawg51

Thanks for the info..I have a Beretta PX4, and a Ruger SR9C, and both of the slides will release with an empty mag in them. This is my first 1911...I guess maybe they're just a different animal...Again, many thanks.

Hey don't worry also if your empty brass looks a bit distorted. both my c-3s did that till they broke in. Best of luck with your new gun! The more you shoot it the better you'll love it too!