Not an M-4 profile, but still 14.5":
14.5" Sabre Defense M-5 middy with pinned KX-3
Midwest Industries SS-12 free float
Magpul ACS stock and MBUS sights
Primary Arms Micro Dot sight and QD mount
I built it for my wife, hence the "Mamma's Fire Pig" engraved into the buttstock. She hates it though, so it's pretty much mine. Glad I didn't paint it pink.....