BudsGunShop.com - Barrel changing...

Doyle, NO. The 500A made in 1960 with the aluminium trigger guard does have a heavier barrel then the modern Mossberg 500s. The original Mossberg 500 and the 500A use different barrels. If you have a 500A, you can not use a 500 barrel on it, or it's barrel on a 500.

I've always thought The 500's interchanged barrels but for the tactical with extended mag tubes. Sending a e-mail to the Mossberg company will tell for sure. Have the serial number close should they need it. If an acquaintance might have a newer 500 or a sporting goods shop may have one to compare.
Look into these solutions before ordering. Most likely its returnable if it doesn't fit then you can tell us all about it

Doyle, yes Sir, 99% of the Model 500 barrels will interchange.