Instructions
Unload the revolver completely. Visually inspect the cylinder to ensure that no ammunition is present.
Set the revolver on its side -- either right or left. Look on the side of the frame -- where the barrel meets the frame -- just in front of and slightly above the cylinder face. If your barrel is pinned, you will see the small round pin slightly protruding in this area. The pin may be blued or finished just like the weapon, to help blend in. These pins are typically 1/16 inch in diameter.
Check the year the revolver was manufactured. This information can be found in your manual or on the bill of sale. Pinned barrels were discontinued by Smith &Wesson in 1982, though still manufactured until parts depleted in 1984.
Check your exploded parts diagram on your owners manual. The diagram will indicate a barrel-pin if so installed.