I bet that there is a ring of broken-off cartridge case, or of some other foreign material, in the front end of your pistol's chamber.
Take the gun completely apart and, using a light, carefully examine the chamber from front to back.
Next, with the barrel still out of the gun and completely separate from it, and pointing muzzle down, try to drop a factory-loaded round into the chamber.
If this round doesn't fully enter the chamber of its own weight, there is something seriously wrong with the barrel.
If that trial round does fully enter the chamber of its own weight, check the slide's breech-face, and also under the extractor hook, for well-attached crud that can be scraped off (or out).
If none of that works, see a gunsmith. If I had your pistol in my hands, I could decode your problem in a couple of minutes, but such is not the case. A real gunsmith will be able to find the problem pretty quickly.
Could your gun somehow be chambered for the .45 GAP cartridge? Check the barrel and slide for markings. The .45 GAP is just a little bit shorter than the .45 ACP.
Did you have any trouble at all, chambering your first batch of Golden Saber cartridges? Did any of them eject sluggishly, or make a "funny noise"? Maybe that was the point when something broke off in the chamber.