I guess Serbu got together with a YouTube celebrity Royal Nonesuch. If your a Youtuber and follow a few of the gun guys out there you have probably seen a few of this young kids builds. Fun and easy slam fire shotguns made from iron pipe and the "such" including a homemade 4 barreled, chest mounting 12 gauge slam fire shot gun.
I guess that's the reason for the RN designation in the RN .50. Serbu known for building more affordable BMG rifles figured hey this kid has something to give. So he brought him in for advice on building a functional bare bones and easy manufactured 50.
The reason Serbu got involved was after Royal Numbnuts tried to make a 50BMG out of a Mossberg barrel some grade 8 bolts, and used some keystock for 'locking lugs.' Well, guess what the keystock sheared like it's designed to, and the kid would have been killed had he not fired it remotely. This kid is actively encouraging people to replicate his builds, and was getting increasingly reckless and/or illegal in his builds (his little 'shotgun arrows' are almost certainly classifiable as SBSs).
Regardless what some people may say about Serbu as far as his production schedule, he is as far as I and everyone else can tell, a very nice guy who cares about his work. Numbnuts was about to make the evening news building the same caliber of rifle that Serbu is famous for, so Serbu decided to 'collaborate' (i.e. design, build, test, and produce entirely himself) with the kid on a cheapish BMG that at least wouldn't kill anybody for exploding. It's a screw-on breech affair, very much like the notorious Hesse/Vulcan/Blackheart rigs, only I'm sure Mark will bother to actually heat treat the bolt unlike them.
Mark Serbu has a history of weighing in on homebrew heavy-cal builds on some of the gun forums, graciously lending his expertise where he is able (and in my personal case, in the form of a 'drop' 50cal barrel cutoff for a very generous price). This is basically what he is doing with Numbnuts, helping him build something worth building, rather than getting impaled by a tubular bolt member keystocked to a much heavier BMG barrel (even firing the gun remotely, the fact he was behind it was incredibly stupid, and that bolt could have easily made it back to his position)
Personally, I don't get it. The kid is obviously high or something in most of his videos, but he does get lots of views (as do many stupid things) and was threatening to become someone of 'prominence' in the build community. I can't tell all of you how destructive that is, so I'm glad he found a mentor/guidance counselor in the form of Mark, who will hopefully steer him to more impressive and productive pursuits (like a job, maybe
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Like the idea of a 50 BMG under $1,000. It basically looks like a barrel with a firing mech though,,,
Pretty much all it is. That's why it is cheap, and wildly impractical for anything but noise making (okay, maybe hunting I suppose)
You're basically putting a pipe bomb a few inches from your face.
Welcome to firearms, specifically high power firearms. The only difference from a pipe bomb is only one end is constricted, and things are much thicker/stronger. That's it! Which is why you can't afford to be close with a 50BMG; it will kill you if that breech fails. It was clear that Numbnuts was eventually going to jerry-rig something that held for one, two, or three shots, then try to fire it up close & kill himself or someone else when it grenaded.
Mark had an accident early in his career and swore he would never let it happen again. So if he's getting involved in someone else's design, I'm sure it will be 100%.
I didn't know that; I'm positive that's exactly what is motivating him here. It was clear as day to everyone paying attention this kid was gonna end up hurt, probably within a matter of weeks, playing with this stuff. For chrissakes, a BMG held closed with 1/4" keystock on this one, and a black-pipe overbore 'barrel' in another (Destructive Device, btw)
Not sure what the fascination with garbage guns is, must be like a rat-rod thing. All I do know is that a lot of newbie builders without any sense started promoting this stuff as viable right around the run up to and release of Fallout 4. Total coincidence, to be sure.
TCB