I built my 300BLK about a year ago, after trying to collect parts during the 2013 "panic". Price was less a priority for me than quality, but I was willing to compromise to some extent depending on what I could find. I stayed with well-known names, though.
I've never heard of your chosen upper/lower receiver, so I can't speak to its quality. You'll find, though, that there are 4, maybe 5 actual manufacturers of AR receivers, and they do castings/forgings to the specifications of who orders from them. I went with a matched set of Mega A3 (flat top) receivers, they are one of the "4 or 5" who make for other brands.
I chose a Rainier Select Match barrel (16", 1:8.5 twist) with carbine gas. They are made from Shilen blanks.
Flash supprssor is an AAC, threaded for an AAC sound suppressor (if I ever go that route)
My BCG and bolt is an AIM Surplus nickel-boron M-16 unit; same material as a Spike's Tactical, grade 8 gas key hardware, properly pinned and staked. Charging handle is a VLTOR BCM Gunfighter, with an extra large latch release. Lower receiver hardware is all CMMG. I started out with a CMMG single-stage trigger, now have a Geissele DMR High Speed National Match 2-stage.
Gas block is a low profile Wilson Combat adjustable, with a Wilson Combat straight gas tube. Forend/rail/barrel nut is a Geissele Super Modular MkII, 13". Buffer tube is a milspec Magpul with a Magpul ACS carbine stock. The pistol grip is a Hogue.
Sights...... my purpose for this rifle is part plinker, part point defense, short to mid-range. I wanted something that would work up close as well as out to about 150-200 yards, that I could hit a man-sized target with at that range. If I put them in a small plate-sized circle, so much the better. I went with a Redfield Counterstrike reg/green dot 1x, with an integral laser. The laser sits below the sight line of the optic, and above the barrel, so BUIS has to be offset so they don't block the laser. I went with an inexpensive offset sight from Black-Ops Tactical (Amazon .com). They have an A2 style rear windage and elevation, with small and large aperture, and work great. I have the BUIS zeroed for 50 yards, the laser for 50 also, and the 1x dot sight (has a 3 MOA dot) for 150 yards. I can't remember what brand the light is, but it's a 500 lumen, and it will light up a target out to 100 yards easily.
After a year of use and maybe 1500 rounds through the gun, only three failures to feed, all due to improperly sized cases (my reloads, my bad. Problem corrected). With a spotter, I can walk the POI as far out as 300 yards shooting steel silhouettes. I generally use 30 round P-mags. My total cost was around $1600, so it wasn't a cheap build, but it's a quality one.
