So I am in a little situation I bought a used generic Mossberg 500, It works great has a houge pistol grip and I added the front houge pump grip because it still had the factory wooden one when I got it, I noticed when I purchased it that the barrel is cut down. I was looking at it today and thinking it looked a little short to be 18" inches, and I know most folks leave the extra 1/2 inch just in case. So I pulled out the measure tape and sure enough the barrel is under 18inches!!! I am thinking of threading the outside of the barrel and putting on a muzzle device to add an inch and make it legal. My question is the measuring point of the barrel, I measured the barrel when it was installed on the shotgun because I am thinking that is the correct way to measure, from the receiver to the tip of the barrel. I feel like I kinda got screwed but I got the shotgun for $150 bucks, and am trying to avoid buying a new barrel. What are your thoughts? thanks in advance for the info. and pointers.