My brother is in the market for a 9mm and really likes the Glocks. He found this MechTech system thingamajig that allows you to swap out the "upper" part of the pistol with a new assembly that includes a 16+" barrel. MechTech says that then you have a long barreled pistol, at which point you can attach one of their stocks to the long barreled pistol, thereby turning it into "shoulder stocked pistol". Okay, seems fine - but can you then remove the stock and then remove the replacement "upper" and put the original Glock "upper" back on and have your stock weapon again, or is that illegal? Here's the link: MechTech Systems My concern is that stocking a long-barreled pistol makes it into something else in the hard and cruel eyes of the BATFE, and taking the kit off again might be somehow illegal. I don't want my brother or I to run afoul of the law. For what it's worth, he lives in Washington but is planning on moving to the Portland metro area in about a year (so it might get to live at my house in the interrim if it's one of those "okay in Oregon but not in Washington" sort of things). Also, I'm not sure what he thinks he'll be gaining other than a choice of what to shoot on a particular day - tinker-toys for grown-ups and all that. I told him to buy his Glock, then a folding 9mm carbine from KelTec instead, but this still looks a bit fun.