I live in TX and was kicking around the idea of getting a BAR parts kit from Sarco Inc (its all the parts minus the receiver).  As far as i know, this would not be an issue as the government considers the receiver as the actual gun.  

Okay, now lets say i'm lucky enough to find a working BAR receiver for sale that was made post 1950 (would not apply as C&R).  Even if I made it a semi auto or single shot, the ATF would still see it as a MG, right? ("once a MG always a MG") Now assuming they consider it a MG, what hoops would i have to jump through to legally take ownership of it (if possible)?  Also, would this question give a different answer if the receiver was purchased IN state? I'm open to any comments or suggestions.  Thanks...

If it's registered as a machinegun, and is transferrable, you just have to through the rigamarole of any other MG purchase - Form 4, 2 sets of fingerprints, 2 photos, $200 check to ATF, and get your sheriff to sign off that you're not a criminal.  3-4 months later, you get your full auto BAR receiver and can assemble the parts kit to it, slap in a mag and dazzle everyone at the range.

If it's not transferrable, you can't have it.  Buy a legal semi-auto BAR from Ohio Ordnance instead.

If you're a type 07 FFL (manufacturer) with a Class 2 SOT, you can make your own full auto receiver and make that parts kit into a post-86 dealer sample MG.

If you can find approved semi-auto plans, you could conceivably machine your own semi-auto receiver to assemble a parts kit on - but the only semi-auto BAR receiver I know of is from Ohio Ordnance, and they don't sell plans or receivers, just completed semi-auto rifles.