In the past, up until about 2005 nowhere existed precision AR parts like today, however KAC did manage to produce better designed parts then anyone like their legendary free-float FF RAS forend, 2-stage trigger, flashlight rail mount, SOCOM baffled suppressor with quick attach that no one else had. They also produced the only quality AR10 matched upper and lower receivers. These important advances became staples to every tier one military and government unit and is largely why KAC became such a dominant military contractor.
Since, KAC has become a marketing force by creating all these flashy components just for the civilian market like catalogs, a new website and the $400 inconel muzzle brake which created huge buzz on AR15 and M4Carbine forums. I was luckily to be given one and can report it improves upon nothing. Even their a-hole approach to customer service helps…its all part of the image. Aside from all that crap, they still manage to improve upon some components for specific uses that most civilians will likely never encounter BUT still some guys just have to have these parts.
If you want to build the ultimate AR out of what is considered best of the best, anything CNC'ed is better then forged. It's also hard to know who makes what these days since there are so many new manufacturers. Big players like Abrams Airborne who own Vltor Weapon Systems make 100's of parts that are rebranded to many companies like Bravo, Troy, Magpul, etc. On a side note, Bravo will soon R&D their own parts by hiring Vltor founder Eric Kincel to head the new venture…should be interesting since Eric is one of the best weapon component designers in the industry and was Reed Knight's former right hand. Eric is well known for designing many of KAC's best selling parts and as Stoner's partner in creating the SR25.
If want you a high-quality precision already built AR15 rifle, LaRue Tactical Stealth is a step in the right direction. KAC SR15, LMT, Noveske, Daniel Defense, Yankee Hill, etc. These are all companies that have been around for a while. Spikes Tactical is newer but uses some of the best industry precision components that are 'other manufactures' rebranded under his name. The better way is to research and source together the best parts and get a gunsmith to build it for you, buy from someone like ADCO or build yourself. Building one yourself is a great learning experience every AR owner should do.
Below is a list of what I consider the best parts out there. I own parts from all the companies I suggest and have lengthy experience using them in custom builds and shooting. I have also owned all the stuff I say is crap too. I never suggest buying anything I do not have personal experience with. I will just cover major parts and will omit piston systems since that wasn't the question asked. If you have any questions PM me, I'm happy to answer them.
Magpul, Mega, LaRue, Seekins Precision, Spikes, POF (or Hogan which I do not own) make the best lower receivers I've found. They are all machined out of 7075-T6 billet block aluminum. If buying KAC you have to be careful, I have SR-15's from 2002-2006 that all have LMT receivers marked KAC so, in that case you pay more for a name. I don't know when Knights started making their own but, the ones I bought in 2010 have KAC made receivers which are forged and then machined. Aside from KAC, I never buy forged receivers anymore, in fact I've sold everything forged I owned...It's just not as good, rigid or straight. For upper receivers the same companies for lowers apply including, Vltor MUR, Centurion Tactical and Sun Devil. I need to mention the Mega, Vltor VIS and LMT monolithic systems too. For forends KAC and URX rails, LaRue, Daniel Defense, Vltor, Troy, MI and PRI which no one seems to use anymore but is a excellent fiberglass rail used on the MK12 MOD0 SPR. For a lightweight alternative, the two-piece (clamp on) super super easy to instal Vltor CASV not only looks cool but sheds a ton of weight.
Barrels are individual preference, I like Lilja, Boots Obermeyer, Steve Satern, Gene Barnett, Mike Rock, Shillen and Noveske (which is actually PacNor). All these guys make stainless barrels as those are what is considered precision. Chrome lined are cheaper and don't last as long, Melonite is a marketing ploy and there is zero proof nitride is better then Chrome. Polygonal barrels have become a hot topic and there is a lot of deceptive infomation out there since there is "polygonal rifling" which is distinctive from "polygonal bore". Both have advantages and disadvantages. The PacNor/Noveske "polygonal", various makers of "5R", Shilen's "ratchet rifling", and others are examples of "polygonal rifling" which are just rifling lands made without the square corners of traditional lands and grooves. What most people think of when they hear "polygonal" though is "polygonal bore", which is a bore with no distinctive lands or grooves. Some venders will attempt to sell you a fitted bolt with your new barrel for extra money, this is BS... don't fall for it. As for chambers my preference is Wylde which allows 556 ball ammo and 223 without feeding issues. I've found that virtually all ammo runs well in a Wylde. Also what has come to be known as the Noveske chamber is pretty good to.
For BCG's Young Manufacturing makes probably the nicest (Spikes uses these). For budget builds LMT is the way to go and for gucci builds JP Enterprises. If you are running f/a which is what the LMT enhanced bolt is for and what KAC improved upon with their enhanced bolt, that is the way to go but don't spend extra money buying LMT's enhanced over their regular less expensive BCG believing its better made - its "enhanced" for f/a only. FailZero is junk, I have one and it never functions right and jams repeatedly in f/a.
For gas blocks KAC, LMT, PRI, LaRue and Vltor. There are some made from composites but they're pricey and totally unnecessary. For charging handles I only use PRI. For iron sights I like Troy, KAC and LMT. Triggers are preference by single or two stage. I like Geissele but also own the excellent Chip McCormick Tactical Trigger which is superb. I also own Timney, KAC 2-stage only and JP. For extension tubes I only buy mil spec LMT, LaRue and own several older Vltor's but the new Vltor's are outsourced to DSA so I'd stay clear of those. Most AR's on the planet have CMT/Stag or Colt. Regarding your question on staking the castlenut, I think its unnecessary and makes it so you cannot change out parts. Back during the expired assault ban, manufactures did this so consumers couldn't install collapsable stocks just as they staked muzzle brakes so suppressors couldn't be used. I have some AR's with staked nuts but the majority are not. All you need is Lock-tight on the threads to keep if from coming loose. For sling mounts I only like Duane Deiter's front and rear mounts. I was trained by him in '99 and '03 and became attached to a lot of his excellent designed products, including his vertical grip but had to replace it with TangoDown's for weight drop. If you want a serious chunk of weight on your front rail his grip is the finest, will outlast all others and reduces recoil climb. For lower hand-grips there are so many but a lot of people like Magpul and, Houge which is nice and rubbery feeling. Before those existed I grew attached to Sierra Precision's and if you have big hands, an SPR or like to benchrest shoot this is the grip to get.
Like RW said, LaRue makes the best scope mounts so don't even consider anyone else's. I'll give you an example, back in 2005 I along with others ditched the use of MK12 SPR's in favor of a smaller version known on the internet as a RECCE with a Gen 1 KAC URX rail. The problem with this rail is that you cannot install it without a special KAC alignment tool that was expensive and quite scarce at the time. Nobody knew anyone who had one. Removing it wasn't the problem, putting it back on was and without the special tool and a vise, the next best thing was a LaRue scope mount which perfectly held the pieces together to be attached. LaRue goes to great lengths to ensure every mount is to exact tolerances for straightness.
You can stake your life on everything mentioned above.
Now you can spend a lot less to have equal fun. Some of my most enjoyable AR's were from much simpler builds with less expensive components for both semi and f/a. Below is a image of a commando 10.5" barrel upper I built in 2004. It consists of a LMT stripped upper assembly which at the time cost $289. It includes upper receiver, chrome lined barrel, LMT M4 sight post gas block and tube. I added a KAC M4 forend, LMT/Crane rear sight, Aimpoint with PRI mount, Deiter sling mounts and vertical grip, LMT ext. tube kit, LMT SOPMOD stock, LMT enhanced BCG with Crane O-ring mod, LMT Defender lower with LMT single stage trigger (I have since installed a McCormick Tactical trigger), Sierra Precision grip and Surefire M950XM07 with paddle switch (old style) all for less then $1000.00. Those were the days!
If you are willing to put in the time to properly break-in a chrome lined barrel you will achieve that same accuracy of a equally sized stainless.
Happy building and shooting!
