Hmm, interesting, I am all for tunned mags for max capacity. But, I have a large number of stock 140 tubes that ran perfect from the start. I put some grams guts in them and a dawnson +1 pad and went to a match. Now those mags only run 22 rounds and my tunned mags hold 24. I have taken stock SV 170 tubes and done the same thing and get a reliable 29 rounds. When you want every last fraction of a mm to get the most rounds in a mag, then get it tunned, but I don't think they are that bad from the factory. If you are having gun function problems, try a tunned mag.