Couple years back Green Mountain was having a decent sale so I ordered a dozen or so barrels. Some of the barrels were their 1" 9mm blanks http://www.gmriflebarrel.com/9mm-bla...k-17-x-1-1-10/ At the time they were $33 with 25% off if you went over a certain dollar amount which I easily reached. A 1" blank isn't big enough for the 1.170" collar that the barrel needs so a lug-less extension was made from some 4150 steel and hardened. Went with 13/16"-24tpi for the barrel and extension threads and put the joint for the two pieces of steel just past the outside edge of the bevel on the barrel. For the chamber bevel/feed ramp I just copied a Sten MKII barrel and cut it with the compound set at 33 degrees. I had a Car type handguard set Delta assembly and a spare front sight base in the parts bin to use also as well as a A1 type upper that had a chunk of the barrel index pin slot missing. Since it was broken I got the upper at a great price (free) so the most expensive part by far was a $100 bolt that was on sale. Since the index slot was broken out on the upper and I was making the barrel an index slot was cut at 6:00 on the upper nose and the index pin was installed at the bottom of the barrel. If at some point I want to put it on a standard upper the lower pin can be removed and another one put at the 12:00 position. Here's a couple pics of the progress and the initial test fire. It has since been parkerized and shot quite a bit.