1st not mine but a project that my Dad and I made.
Gonna answer some questions all in one post:
1. It is a RRA dedicated 9mm lower. While from the out side it looks like a 5.56 magwell it is only broched for a 9mm magazine. DDLES and Lone Wolf are the only manufacturers of 9mm lowers where the magwell is shrunk to 9mm size. Both companies are too slow and too ne to be used with any reliability, milling out for the Lone Wolf took it out of the running early. I too like the idea of swapping the upper but I have seen too many issues with mag blocks to force me not to go that route. Most mag blows seem to need to be tuned to that weapon.
2. The sight is an ATN Digital Ultra Sight. It is a complete POS and should be used as a target than a sight. While it worked when we shot it, it now just collects dust. I do not recommend it.
3. SBR (short barreled rifle) means exactly that. The barrel is less than 16in. Before assembling the rifle you must send fingerprints, pictures, and ATF Form 1, and a 1 time check for $200 the the BATF and E. after a few months they send you a stamp that makes it legal. And then you have fun. No you cannot make it a machine gun, in fact you cannot make any gun a machine gun. There are machine guns out there but they are exceedingly expensive.
Our next project is a 11.5in. 5.56 SBR based off of a Black Rain Ordinance Reciever.