A photo of the revolver would be helpful. Also, assuming you measured the barrel correctly (from the cylinder face) and it measures 5-inches, you should send to S&W for a factory letter to see if the 5-inch barrel is original to your 28-2. If it is a factory original 5-inch the $50 for the letter will be a good investment. If not, then at least you will know what the original configuration of the 28-2 was. Click on Downloads at the tope of the screen and then of factory letter request form.

Bill