I'll kick this around one more time.... this is what sits over my bed's headboard
do your homework on the legality of shouldering an AR15's PISTOL's buffer tube without anything like a brace or blade attached...BATFE has waffled on the brace and to me it is not worth the headache.... obtain a buffer tube that is long enough to allow you to hold as if it were a rifle... a rifle length is a little too long for me, and if you choose a factory adjustable, find some way of preventing a butt stock from being attached, like drilling and tapping a sling swivel... I wouldn't use an adjustable tube.. a KAK super tube is just right for me
purchase a complete lower, new from manufacturer and make sure the ATF 4473 is marked "other"... PSA has a lower with a blade and KAK tube
purchase a complete upper from manufacturer with a 7 to whatever length barrel you want... I like front sight tower and carry handle sight and a 10.5" is just about right for me... add a flashlight
remove the buffer tube that came with the lower if necessary, and replace with the longer tube
if you are feeling froggy, add a rubber end cap... it is not that uncomfortable to shoot without anything
test fire it with cheap Russian ammo, and if it cycles with that, you are probably good to go...you may need to change buffers....mine is loaded with M855
you don't have to worry about the legality of a brace or blade, if you don't have a brace or blade YMMV
mine shoots a little over 2" with 69 Sierra Match Kings and scope at 100yd... about that at 50yd with open sights and M855