The AR-15 has the biggest aftermarket of any rifle platform ever made. Thousands of parts, hundreds of brands, and because the platform is built on a widely shared standard, most of it interchanges. That’s the good news. The bad news is that a catalog full of options doesn’t tell you what’s worth buying. I’m Lance Rankin, owner and gunsmith at Western Sport in Roanoke, Texas, and I’ve spent years assembling, repairing, and upgrading these rifles on my bench. Here’s how I think about the major parts, and where your money actually goes to work.
Receivers: forged or billet
Every build starts with an upper and lower receiver, and your first real decision is forged versus billet. Forged receivers start as aluminum blanks hammered into dies, then machined where it counts. They’re strong, light, and affordable, and for most builds they’re all you need. Billet receivers are CNC machined from a solid block, which allows tighter tolerances, matched upper-and-lower fit, and sharper looks. I machine a billet matched receiver set under my own Rankin Industries brand, so I’ll admit a bias, but I’ll also tell you straight: buy billet for fit and finish, not because forged is weak. It isn’t. My full upper receiver guide goes deeper on this choice.
The barrel: where accuracy lives
If you only spend real money on one part, make it the barrel. Nothing else on the rifle can shoot better than the barrel allows. For a general-purpose carbine I like a 16-inch tube with a mid-length gas system, a 1:8 twist, and a nitride or stainless finish. That’s exactly the recipe behind the 16-inch SOCOM mid-gas barrel I developed with Faxon Firearms: button rifled, QPQ nitride inside and out, NP3 coated extension, 11-degree target crown, and every barrel magnetic particle inspected. Caliber is its own conversation; if you’re torn between the two most common options, my 5.56 versus 300 Blackout comparison will sort you out.
The bolt carrier group: the heart of the rifle
The BCG does the hardest work in the gun, and it’s the part where cut corners come back to bite. What I look for: a carrier machined from 8620 steel and properly heat treated, a chrome lined interior, a gas key staked with Grade 8 fasteners and torqued to spec, and a Carpenter 158 or 9310 bolt that’s been high pressure tested and magnetic particle inspected. An improperly staked gas key is the single most common failure I fix on budget rifles.
Coatings are where BCGs have gotten genuinely better in recent years. A slick modern coating sheds carbon, runs cooler, and cuts down on lubrication needs. My Rankin Industries SP4 coated BCG is my answer to that problem: it wipes clean with a dry cloth and runs without oil. If you want the full rundown of phosphate versus nickel boron versus nitride versus DLC, read my BCG coatings guide.
Trigger, charging handle, and buffer
The trigger is the part you feel on every shot, and a rough mil-spec trigger hides how well your rifle can shoot. You don’t have to spend big, though. The SP4 coated trigger group I offer takes a standard trigger and makes it noticeably smoother; plenty of customers tell me it saved them from buying a pricey aftermarket unit.
The charging handle is the cheapest upgrade that changes how a rifle handles. An extended latch or ambidextrous design makes a real difference under stress, with gloves, or when running an optic with a big eyepiece. And don’t overlook the buffer assembly. The buffer and spring inside the tube absorb the energy of each shot and feed it back to cycle the action, so a correctly weighted buffer smooths recoil and keeps the rifle running reliably. A basic mil-spec buffer tube kit covers most builds.
How to choose without going broke
My honest advice after years of customer builds: decide what the rifle is for before you buy anything. A home defense carbine, a precision gun, and a range toy want different parts, and the internet will happily sell you all three at once. Spend on the barrel and BCG first, the trigger second, and cosmetics last. The platform’s interchangeability means nothing is permanent anyway; you can test a part on one rifle and move it to the next build.
If you’re starting from scratch, my step-by-step AR-15 build guide walks the whole process, and my 15 best AR-15 upgrades post ranks where the money matters on a rifle you already own. Stuck on a parts decision, or want a set of experienced hands to assemble and headspace it? That’s what I’m here for. Email [email protected] or call 817-393-4000.
Lance Rankin is the owner and Chief Gunsmith of Western Sport, a family-run Type 07 FFL and Class 3/SOT dealer in Roanoke, Texas, serving shooters since 2007. Born and raised in Texas with over 50 years of experience handling firearms, Lance purchased Western Sport in 2017 and turned his lifelong passion into his profession. He specializes in AR-15 and AR-10 platform rifles, manufactures Western Sport’s own AR-15 line under the Rankin Industries brand, and runs the shop’s in-house Cerakote coating operation. When he’s not behind the counter or the workbench, you’ll find him on his ranch deep into the night, hunting coyotes with an AR-15 and thermal optics. Lance holds an MBA and personally shoots and tests the products Western Sport sells.
