All depends on what exactly someone wants.
RRA, POF, DPMS can take a couple months.
Some CMMGs take a couple months.
Olympic, Stag, J&T are a couple weeks.
I currently have M4's, 14.5" LW midlengths, 16" LWs, 16" midlengths, and 18" midlengths on hand.
16" midlengths have been a real Mothfookle for a while now. But they have been working hard to correct that.
The 16" lw midlength barrels were way behind schedule. CMMG finally has some on hand I have ordered a number of complete uppers and they should be here in a week.
The 16" MLs regular profiles were on a multi month back order. I finally got in some yesterday. Same goes with the ML free float. YHM has been out for awhile. But I found a retailer that had a couple and bought those.
When it comes to ARs I can do single small parts all the way to complete rifles, and everything in between.
I sell J&T kits and uppers for about 50$ less then you see listed on their sight. I 'make' complete -receiver kits for all manufacturers.
The easiest thing to do is find what you want, tell me the manu and part and I can get you a price and time.
DelTon, MA, M1 don't do dealers so buy direct.
Pete