When I decided to build a rifle, I sought the advice of those builders more experienced than I, and boy did I get an education in a hurry.
I was quickly introduced to some of the modernizations that have come up in the last several years that neither Stoner nor the US Army Ordnance Department ever dreamed of. Of course, a change in upper doesn't usually cause such a ripple effect in your parts selection but it does when it's a drastic departure from a standard mil spec upper.
Aero Precision M4E1 Enhanced Upper
Before I fell subject to this marketting slang, I asked very directly what the benefit was. Aero's M4E1 upper already features excellent machining, a flat top picatinny rail for optics mounting, and comes in at a very reasonable price tag. The "Enhanced" upper completely redesigns the barrel/handguard mounting interface in the name of additional rigidity and strength, picking up where Stoner's design and the many workarounds (attempts to integrate free float handguards into the legacy design) left off. By integrating the handguard mount into the upper itself, the stress of that handguard is no longer concentrated on the barrel nut. By taking all of that stress off the barrel nut, it could be made smaller, now only dealing with locating and securing a barrel. And, but reversing the typical arrangement of barrel nut to upper (the upper having outside threads, and the nut threading on) the barrel nut now threads INSIDE the upper and the gas tube no longer passes through the barrel nut. Way beyond making assembly simpler, it gives a rock solid mount for the handguard. To which I mounted....
Aero Precision Enhanced Handguard
Possibly the only downside to using this specialized upper is it restricting your options for handguard. Quite frankly, Aero Precision has you covered with options ready to bolt on in various lengths, diameters, and colors. The Enhanced handguard (M-Lok, anodized black, 15") was my choice, as I had intended from the outset to build a full length rifle and I wanted plenty of rail space and to push the front sight as far forward as practical. Yes, I planned to run an optic, but I am a big believer is making a sight radius longer where practical. Some will tell you it doesn't matter, it matters to me. The handguard features a compatible mounting solution with the Enhanced upper (mounts with 8 screws and a little blue Loctite if you don't like things backing off), anti rotation tabs, and a monolithic rail that matches perfectly with the Picatinny on the upper. I don't care to mount my optics on the handguards, but it's there if you need it. The handguard is rock solid, and fills the hand, though the Quatum may be a better fit if you like your handguard a little slimmer and lighter.
Faxon Firearms 18" Gunner barrel in 5.56 Nato
I had always intended to use a rifle length gas system and an 18" barrel, beyond that I was pretty open to suggestion. I was immediately steered to Faxon Firearms and their Gunner barrel. Faxon is well known to provide a good product at a fair price. Being a Goldilocks build/jack of all trades, I was after a full capable rifle that could still shed ounces where possible and not compromise capability. The Gunner barrel utilizes the "government profile" from the M4E1 extension (with matching feed ramps) to the gas block, at which point is narrows considerably to the lighter weight "pencil profile" for the remainder of it's length. This maintains more material and ability to cope with heat near the chamber where it pays dividends, but removes crucial weight from the furthest extreme of the barrel aiding the rifle in transitioning side to side. Having shot this side by side with my father's traditional government profile barrel, I can attest to mine making a noticeable difference in weight and momentum, with a small penalty in additional felt recoil due to the lower weight. I call it a worthwhile tradeoff for a rifle meant to be carried and shot from the shoulder, not rested on a bench it's whole life. The jury is still out on potential accuracy as I dig into hand loading, but Faxon is not known to make trash barrels. I debated briefly on .223 Wylde, but shelved it for the time being as it didn't really add much to my concept other than price.
Toolcraft Nickel Boron Bolt Carrier Group
I quickly learned that MANY of your big name companies are using Toolcraft as an OEM supplier of their own bolt carrier groups, and I felt no reason to spend more to have someone else's name on the part. C-158 Carpenter Steel bolt, MPI tested, and nickel boron coated (made of good stuff and slicker than greased owl snot) it certainly looked and felt the quality part when it arrived at my house. Now, I fight a neverending battle to keep it clean, typical of direct impingement guns. The nickel boron coating, promised to make cleaning a wipe and go affair, hasn't alleviated the need to soak it in CLP and break out the brass brushes, but it does seam to make the BCG run a little nicer when things get hot and dirty. For the minimal extra money, I don't consider it to be a waste.
Next week, I'll start meandering my way around the rifle hitting all the little things that make a rifle run, since we've gotten the major parts out of the way. Let me know what you guys think and leave me your feedback positive or negative. - Phil Rabalais