All of you worried about "intent" have been misled in my opinion. I k ow plenty out there like to throw around the term "constructive intent" which is a improper substitution for the actual term of "constructive POSSESSION".
The litmus test for this is, do you have a legal use for the items in your possession or can they only be used to construct something illegal. IF you had a carbine buffer tube attached for the purpose of installing a sb15 and ALSO owned a stock body that could be installed on the tube BUT DID NOT OWN another firearm in rifle configuration that COULD accept the stock body; THEN you would be in a bad spot. IF however in the above scenario you owned for example a ar15 rifle that COULD accept the stock body, you are good.
I carry a gun every day. If I also have a ski mask in my trunk and go to a bank do I have intent? NO