Ian, welcome aboard. (ETA: and thanks for sharing your build with the web!) Maybe you are new to homebuilding, but this is only part of the guidance and incomplete information that could lead someone to get in ATF trouble. There has been considerable recent discussion on this topic as the ATF has begun to take a much closer look at homebuilders. As a matter of fact, per ATF2015-1 if you built this at HMG and took it home as your firearm, there is ATF guidance that suggests they are required to log, mark, and legally transfer it to you since they were involved in helping complete the build. (This is primarily in response to California CNC build parties)
https://www.atf.gov/firearms/docs/ruling/2015-1-manufacturing-and-gunsmithing/download
I did not see in the video series where you set the cocking tube depth and bolt gap. Both are critical for proper operation of a roller-delayed blowback firearm. Did you verify these dimensions?
It definitely appeared smother. There were no modifications made to the flat/receiver, which is a huge head start. There are a few Prexis Gen1 flat guns running here in MD, so they are buildable but definitely require a lot of work. I was well aware that they were "prototype" when I made the purchase. I think Prexis is on Gen3.
For $250, I would expect an "LSC quality" flat that can be bent and assembled without any tweaking. I look forward to seeing if HMG's production run lives up to that price standard. If so, I'll probably be purchasing one.
I'm really excited to see homebuilding interest openly growing here in Maryland.
