Understood. It sounds like the original magazine may have been smashed at some point.
Be careful to not stick the forward magazine guide inside the magazine. It's a common problem with shooters new to handling mine; and I believe the primary reason for people running into difficulty with insertion.
But, of course, all of my experience is based on a sample size of one -- which, itself, was damaged, repaired, and modified before any testing.
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I picked mine up at an auction, as well. It was, however, sold as a "parts gun" because it had been rolled over by a horse. The barrel was bent, the fire controls were damaged, and the stock was absolutely shattered. I got it mostly fixed up, and it turned out to be worth keeping around.
Other than the safety*, it works well enough that it actually goes on hunting trips and a couple family members keep asking to buy it from me.
People carrying it do have to keep the two major flaws in mind, though:
1. Don't trust the safety*. Just keep the chamber empty.
2. Rim-lock in the magazine. Incorrect loading, or a slip while attempting to unload the magazine will jam 'er good and proper.
*(My safety was damaged. It's not a design flaw, from what I recall. -But it's been a few years since I had that action out of the stock to refresh my memory. Heck, I may have even removed the safety entirely, just so people wouldn't try to use it. Other people use that shotgun so much more than I do, that I haven't fired it in years.)