Just picked up my Mossberg 500 tactical persuader shotgun. It sounds as though something inside the barrell is?

Whenever you buy a gun regardless if it is new or used you ALWAYS disassemble it and give it a thorough cleaning. And to do that properly, you need to read the manual. A gun is not something you muck around with in hope that you are doing it right. You ALWAYS read the manual FIRST.

One of the things a manual will tell you is how your gun is configured and what if any accessories have come with it. In this case, it could be as others have told you that it may have a magazine limiter. If so, it will also tell you how to remove it.

Your barrel should be a giant empty hollow cylinder. Have you bothered to remove it and inspected it? In fact you should have read the manual and disassembled it to do an inspection yet as the first thing you did. Generally it is good with any new firearm to also do a light cleaning of any manufacturing residue and a light oil/lube (per the manual).

I would say Space Cowboy is absolutely right; It sounds like that would be your mag shell restrictor.

So you either A) Live in a state that restricts shotgun shell capacity, or B) You bought it online and didn't see the state compliance statement.

Either way, it's just a little wooden dowel in there, so if it is legal to do so in your state, there are ways to remove it...

If there is something loose in the barrel, you should be able to point the muzzle down and have it fall out. Obviously you should set the shotgun down and walk away or RTFM about the plug.

Why, YES! Read the flinking manual!! Had you bothered to do so, you would already know about the wooden dowel rolling around inside your magazine tube, as well as how to get it out of there!

If the words are too big for you, you can watch this video on how to do it: http://www.youtube.com/watch?v=Cmy0nwXW6C8 Don't get up, Sparky . . . . I'll get it for you!

The shot limiter is a Federal requirement, but only if you're hunting ducks and other waterfowl.

You need to pull the P L U G.

...probably the 2 shot limiter in the magazine...maybe if you had read the manual first, you wouldn't have made such a rookie mistake....

RTFM