As I understand it, one of the main design parameters for the 300blk was to be fired sound suppressed from an AR platform. Makes a lot of sense to have a big bullet if your working velocity out of a rifle is only 1100ft/s.
The overall picture for my build is the same as yours, 16" tactical rifle. (Long post to come...).
Here is my lower:

-Battle Born billet lower (Not actually class-3/full auto, they just put the extra auto mark on the frame.). I only got this billet receiver because the price was right, I have no problem with forged parts (like the upper I used). This lower does have a really nice magwell.
-Geissele SA trigger. Kind of just wanted to see if it was worth the money. Really nice trigger, but not enough better than an RRA for me to justify the price.
-Magpul enhanced trigger guard.
-IKH SLAP end plate (just in case I ever want to run a single point).
-Magpul MOE stock and grip.
-Other internals are DPMS.
Already pulled apart the upper to send the defective barrel back, but here is what I have for the upper:
-Aero Precision forged flat top upper, DPMS FA and dust cover (I did decide to put the FA on it in the end).
-Bravo Company Gunfighter charging handle, large latch. I wanted a latch large enough to easily be manipulated with gloves, but this large one is a bit too big and will likely cause problems when a sling is used, I will be replacing it with a medium latch. The large latch would be excellent for a scope though.
-Palmetto State Armory BCG.
-Bravo Company low profile gas block.
-Battle comp 1.0.
-Troy Industries Alpha Rail - 13". Awesome rail, if you haven't gotten one already, check these out. Free floated, super easy to install (uses standard barrel nut), really light weight. It has modular rail sections that I did not include in the picture, so you can attach small rail sections anywhere you want while still saving A LOT of weight over a quad rail (I'm not a fan of the quad rails, glad to see they are going out of style). My decision to go with a 13" rail was inspired by 3-gun ARs even though that is not my intended use for the rifle. The long rail allows the user a lot of options as far as grip stretch. The long rail also allows the user to take advantage of the free float in more situations (firing from rested positions). Also, the long rail gives a longer sight radius with irons. Weight is an issue with this build, but my thinking now is that the long handguard offers me a lot for the added weight.
As of now, I am forgoing a vertical grip. I don't like how they feel on non-SBRs.
-Barrel, the barrel was and will be a a 16" midlength gas, medium contour, 5.56mm caliber. The defective one I just pulled off was 416 SS, but I don't have a problem with chrome lined.
-Sights/Optics, haven't got any yet. Big expense (even irons) and wanted to build the rifle first. My plan is a Troy fixed front sight mounted at the end of the rail, Troy flip up for the rear, and a regular Aimpoint red-dot, not sure about the mount. The irons will be either absolute co-witnessed or lower 1/3 co-witnessed with the Aimpoint. Is your patrol rifle's irons lower 1/3 or absolute co-witnessed with your optic? What is your opinion on the setup your rifle is running?
BTW, if you plan on building the upper yourself and you don't already have one, I highly recommend one of these:
http://www.midwayusa.com/product/210021 ... cm_vc=U112
I like the Wheeler one a lot better than the ProMag one. The BCG insert on the wheeler one also has rod that slides back and forth to aid in gas tube-barrel nut alignment, very nice feature.