In order to fill out the paperwork properly you need to at least know what length barrel and caliber you intend to register. Without a barrel under 16" you just have a rifle. With a built Lee you just have a built rifle, but not necessarily a short barreled rifle.
Have the "comp" thread on. Then when you want to use as a suppressor host, just unthread it. You will lose the front sight but he'll you probably wouldn't be able to see it anyhow thru a can.
Go 6" slide with short dust cover frame. 6" guns aren't all that popular because they don't fit in the box.
But here's and idea. Go 5" slide and dust cover, and put a fake comp out on the end of a 6" barrel and tie the contours of the comp into the slide.......6" sight radius
If that's what I had into it and wanted my money back. I might list it at $175 and let someone haggle with me.
The only thing that I sell and make money on is kydex stuff. And that is simply to turn around and buy more materials. I figure my labor at $10 an hour. For stuff I build.
300blk at subsonic speed has about the same pressure as a subsonic 9mm. 300blk is .308 in diameter 9mm is .356 in diameter. The hole is plenty big enough.
So it's Monday, I've got to go too Bass Pro today to meet a guy at 1330. Who wants to get lunch at FTM's place and support him?
Jack's New Yorker at noon?