Hey, n00b!! Just because your pants are on fire to build an AR doesn't mean the rest of us are interested, so quit with the challenge schtick, and by all means feel free to take your grandiose but a wee bit boring AR challenge to another website. PLEEEZE!!!
The original challenge was the Mosin Bubba Build-off, which required people to get a Mosin (cheap at $150) and mutate it as outrageously as possible. I was only peripherally involved with one gun which I later got to shoot, and some creative madman had made the astute observation that the rim size of the 7.62 x 54R was the same as the 500 S&W magnum. So yes, he got a barrel made in 500 S&W, and I got to shoot some of the standard 350 grain Smith rounds, followed by the much more serious 500 grain round that in a Smith will try to break your wrist, to some extremely perverted loads that had 700 grain hardcast lead bullets. So yeah, the same weight bullet as a 50 BMG. That one was a bit stout even in a heavy Mosin. So the gun was cheap, you could get really funky with the design, and people had lots of fun.
With an AR build parts still aren't cheap, and what do you REALLY think you can do that hasn't been done before?? Seriously!! Anything in .223 pistol or rifle has already been done, JPrifles.com has about every useful caliber available, and 6.8 SPC and 300 Blackout are all stock guns. And off the beaten trail, I have crossed paths with Tony Rumore, who is perhaps the most creative and yet perverted AR builder ever, and I have a 50AE AR that he made for me (Yes, Virginia, a real 50 caliber AR...) that is pretty much at the edge of the envelope.
And BTW, Tony went completely off the reservation and made an AR that ran on 32 ACP rounds, so it was an assault rifle for pimps.
And last but not least, check this out Mr. "I wanna stir the pot and build an AR or I'm gonna take my bat and ball and go home":
This is a Siamese M-16 Class III full auto with two back-to-back guns with the gas tubes crossed, so the rifles alternately fire and then actuate the bolt on the other gun. Tony laconically stated that "this is a wild ride".
So be sure and get back to us when you go beyond the edge of JPrifles.com and Tony's inspired madness, and once again, PLEEEZE take your challenge over to whatever forum you are trying to browbeat us with.