Constructive possession question

[rackem1899]

So I picked up my first stripped lower today! During the ten days, I already received my LPK and buffer tube assembly. However, I haven't ordered the actual stock yet (waiting for payday this Friday). Anyways, I'm itching to start the assembly... But was wondering if this would be a no go? As it could be considered a pistol build? I don't know, maybe I'm just a newbie... Thoughts?
I'm already in possession of a M&P 15, but do not have the upper I intend to use for this gun...If that matters

[CSACANNONEER]

Start assembling without fear.