What do you need specifically? I finished one build last month, and just this week got 100% of the parts I need for a second build that I am waiting on the Matrix Aero receivers to do. I didn't end up compromising much at all on either build, nor did I pay more than MSRP. If you want to do it, you can within a few weeks. If you aren't super picky, you definitely can do it really fast. I bet you could get everything on order and received within 1-2 weeks, since I just did it.
For all your small parts: ejection port, forward assist, buffer parts, etc. you can probably use Midway. All of that was still in stock last I checked. Also, depending on what you want for a handguard, they have a lot in stock right now. Same with a lot of other stuff like muzzle breaks, stocks, etc.
What do you want for a barrel? If you are just looking for 16" M4 profile, right now CMT Tactical has a nice one for $187. If you want to spend a little more for a nicer one, SurplusAmmo has some Blackhole barrels for $230 in 16" M4, 16" and 18" HBAR profiles. I just got the 18" HBAR with the midlength gas system and its really nice.
If you need a LPK, they are popping up everyday on different sites. Core15 has a really nice LPK that comes with an upgraded aluminum trigger guard for $75. I just got one and it looks good to go. If you are planning to upgrade the trigger you can save cash and Riflegear has DPMS kits without FCG for $40. PSA has nice kits with upgraded pistol grip and not FCG for $50, or for a really good set of deals they have some lower build kits with the entire LPK, buffer tube/spring/buffer, and stock for $100 (mil type stock) and $180 (Magpul MOE).
All of these companies are shipping within a few days of placing an order. And as of writing this, all the things I mentioned are in stock.
What I'm saying is...the parts are out there. If you are looking for something specific that wasn't covered by what I pointed out, let me know and I might be able to help you.
