I have sold a lot of used barrels in a short period of time and have been asked this question many times. Is it risky buying a used Thompson Center barrel when you don't know how many shots have "gone down the tube"? My answer is "most often" "NO" and here is why. From the reading that I have done for most calibers it takes well in excess of 5000 rounds before you start to see the wear associated with "shooting" out a barrel. Just think about the logistics of that in a single shot rifle! Then when you apply that question to Encore and Contender pistol barrels and then maybe throw in a "hand cannon" round like the 44 Rem Mag, or the 460 S & W and I think you would wear out the wrist of the shooter first! Earlier I said "most often", and I did that deliberately. I have also heard that some high speed rifle calibers like for example the 22-250 are especially hard on barrel life. I guess I could believe that sending a tight fitting projectile down the tube in excess of 4000 FPS would create heat and wear. I also left in the "most often" qualifier in for that rare guy that shoots like there is no tomorrow. That guy that reloads, goes to the range daily, is obsessed with accuracy and performance and most likely knows that gun better than some guys know their wife and kids. You know, that guy that we all want to be when we grow up! You might not want to buy his barrel because he is only selling it because it has literally lost its edge. I think that guy might be 1 in 1000 and that leaves 999 barrels with plenty of life left in them. let's face it most of us change barrels and calibers more often than others change underwear. Thanks for reading and be safe. Marty