This is a 7-round stainless .45ACP factory Springfield magazine for the 1911.
Robert, make sure you have no crease at the top of the magazine if you have tried disassembly with the magazine in. Try upgrading your short guide rod with a Wilson Combat short guide rod and flat wire spring with a Shok-Buff. The standard spring should be a 16 # spring. The Wilson Combat flat wire spring is a 17# spring. This will run you $20 bucks + ship. The upgrade is good for 40k rounds, and runs smoother in my Garrison. The Shok-buff reduces barrel jump and cushions metal on metal. Typical response when the last cartridge is fired and slide doesn't lock open, you should use a heavier slide spring. I've cycled over 500 times and love the action. Try it, see what you think. Cheap fix. I still like using the Springfield magazines. Navigator Tom