My question is this if you have the ability to create your own weapon for your own use for example
AR SBR or  AOW device  are you required to get proper documents for registration before you start to create your weapon built mainly from scratch other than common components trigger parts and springs? I am asking this because what if your idea wont work?  Or do they even need to be registered if you create them for your self?  Example would be the kt15  how many people actually register them with ATF as SBR's or long guns?  

1. Would you need to register a AOW you made from scratch?
2. Do KT15 have to be registered? What im asking is what if you Got stopped by LE and had it in vehicle and it had no serial numbers?

From what i understand on form 1 is it must be done prior to building?

Thats kinda what i thought but what if it was a legal length rifle with out serial number?
Legaly arent they all supposed to have a form one even if its a KT15?

AK 47 are built all the time with reciever starting out as "flats". From what I understand it isn't illegal to build, but it is illegal to sell. Of course it still has to fit leagal standards-barrel length, overall length ect..

As long as the gun is a legal (non-NFA) weapon, you are not required to mark it in any way whatsoever.

Quoted: As long as the gun is a legal (non-NFA) weapon, you are not required to mark it in any way whatsoever.

Correct.