It'll fit if your gun is any of the 500 "tactical" models currently offered. Only the sporting guns went to the shorter slide action tube. All tacticals, if they have removeable forearms, use the 7 5/8". That tube isn't rare by any means, either. Ebay always has a few at any time....but do NOT buy the first one you see! They can range from a low of about $20 to $50+. If you're not in any real hurry wait for a good deal. Midway always has them....well, always seems to have them when you don't need one. Brownells ALWAYS has them but they charge more than any other source it seems. There's also an extended slide action tube adapter put out by Hogue at one time and by others now. It goes $12 and up. Again, wait on a good deal. It's the best economical choice. On the Ebay slide action tubes....word of warning here. There is a new style, the one 99% of us have and never suspect any diff, and the old style that had standoff bushings on the mag tube. Spiral flat springs. The old style is a straight wall tube and only works on the old style tubes. The new style, about thirty years of new style (lol) has dimples pressed into the slide tube. The dimpled i sthe one you want. Dimpled 7 5/8". Some folks call it a 7 3/4" but it's the same tube.
Welcome to the forum, sir!
Richard