BlogsChoosing the Right AR-15 BCG: Factors to Consider

Choosing the Right AR-15 BCG: Factors to Consider

What is a Bolt Carrier Group?

Before we deep dive into our top picks, it’s crucial to unpack the nuts and bolts of a BCG’s operations within the AR-15 framework. Grasping the intricacies of the bolt carrier group components and their synergy is pivotal for troubleshooting and confirming that your firearm demonstrates sterling reliability and immaculate feeding.

So, here’s the lowdown on how an AR-15 BCG goes about its business: teamed up with the gas setup, it cycles, discharges, and jettisons rounds in the thick of action. To whittle it down, the bolt carrier group shoulders the task of chambering a fresh round, ejecting the used casing, and standing ready to do it all over again.

Now, let’s zoom in on the crucial elements nestled within a full-fledged bolt carrier group and their contributions to the overall dance:

Firing pin—Post trigger engagement, the hammer performs a swift pivot forward, connecting with the firing pin. This pin then makes contact with the primer of the round that’s nestled in the chamber, leading to the firearm’s discharge.

Carrier aka gas key—Perched atop the BCG, the gas key extends a handshake to the gas tube. Post-bullet dispatch from your barrel, gases high-tail it back via the gas key, swooping down into the bolt carrier group’s core.

Bolt carrier—The very chassis of your BCG. Bathed in high-velocity gas, this chamber propels your BCG backwards, coaxing the buffer and its spring to compress. A nod to the rigors it faces, you’ll notice bolt carriers and bolts are engineered from robust ordnance steel to weather extreme temps and pressure.

Bolt—Sporting locking lugs that play a game of twist and shout to secure and release the bolt within the chamber, as the bolt carrier retreats, the cam pin gives the bolt a spin, disengaging it from the chamber and greenlighting the BCG’s retreat.

Bolt gas rings—These triple rings take their place at the bolt’s aft, casting a seal twixt the bolt and its carrier, corralling the gas expansion within the BCG’s heartland.

Extractor—This component latches onto the casing’s rim, whisking it from the chamber post haste.

Semi Auto vs. Full Auto BCG

When it comes to AR-15 bolt carrier groups (BCGs), you’ll typically encounter two primary types: the semi-automatic BCG and its full-auto counterpart.

Now, don’t leap to the conclusion that slotting a full-auto BCG into your AR-15 will morph it into a high-octane machine gun—it’s not the case. Interestingly enough, the majority of AR-15s up for grabs in today’s market are actually paired with a “full-auto” bolt carrier group, and it’s perfectly aboveboard to utilize one—no legal hullabaloos to keep you up at night.

Diving into what sets them apart, the distinction zooms in on the configuration of the carrier. Full-auto carriers flaunt a beefed-up rear lug, the sole purpose of which is to buddy up with the auto sear on an authentic full-auto rifle, setting off a symphony of rapid fire. However, in the realm of a semi-auto AR-15, this feature just comes along for the ride without contributing to the performance.

There’s a perk tipping the scales in favor of the full-auto BCG—it’s got a bit more heft. Tipping the scales at about an ounce heavier than its semi-auto cousin, this surplus in weight can be a boon to your rifle’s reliability, given the specific build and temperament of your setup.

Think of it like opting for a beefier buffer—shifting up from a carbine buffer to an H buffer, or from an H buffer to one that’s H2. It’s a subtle tweak, but sometimes, that’s all it takes to smooth out the action.

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Aero Precision Nickel Boron BCG

The Aero Precision Nickel Boron BCG stands unsurpassed as our premier selection for an AR-15 BCG. The Nickel Boron finish embodies cutting-edge coating technology, delivering not just exceptional durability but also a notably smooth action.

In the military landscape, Nickel Boron’s prowess is no secret—it’s the preferred choice for coating 60 mm and 81 mm mortar tubes in the Army, the hoists of Blackhawk helicopters, and on select naval vessels that demand rigorous performance.

For those keen on aesthetics, Aero presents their Nickel Boron BCGs with an option to sport their logo or to keep things understated with a non-logo variant. Should you opt for the logo-adorned version, you’ll find the craftsmanship tasteful and refined, adding an elegant touch to your BCG.

Aero Precision Black Nitride BCG

Switching gears to the Aero Precision Black Nitride BCG, this option rises as a stellar upgrade, frequently sought after for its enhancements over the standard mil-spec offerings. The nitride finish, renowned for its incredible hardness and smoothness, promises ease of maintenance and a consistently slick performance out of the gate.

Choosing this Black Nitride specimen from Aero secures you the esteemed Aero quality, along with a performance that nudges close to the slickness found in Nickel Boron, all while easing the strain on your wallet. The decision between a logo-emblazoned model or its more discrete counterpart remains in your capable hands.

BCG Finishes and Coatings

The market is practically brimming to the gills with an overwhelming slew of coating options for bolt carrier groups these days. But here’s the skinny – it’s probably not as critical as you might wager.

Take your run-of-the-mill phosphate finished BCGs, for instance; they’ve been clocking in reliably ever since the AR-15 first made waves.

Cue in the Military Arms Channel. They’ve gone ahead and put a BCM AR-15 through the wringer, churning out more than 7000 rounds – no cleaning or fresh lube, and not a single hitch to report. All that, powered by none other than a standard phosphate BCG.

So, then, what’s the draw to anything else if phosphate BCGs demonstrate such top-notch performance?

Well, other contenders in this space – Nitride, Nickel Boron, you’ve got DLC coatings too – they’re a cakewalk to clean. They boast smoother surface finishes that, in theory, would stand up to the elements a bit more stubbornly, keep chugging along with fewer oil baths, and stick it out longer with nary a whimper about maintenance or rust.

Hard Chrome

Rewind all the way back, and you’ll find the firstborn AR-15 bolt carrier groups received the hard chrome treatment, all thanks to Eugene Stoner’s directives.

Chrome earns its stripes in the gritty battlefield where bolt carrier groups earn their keep. Relentlessly hard, it’s a tough nut to crack wear-wise. It fights off corrosion with a vengeance, and its naturally slick charm doesn’t go unnoticed.

But now, we’ve got a bevvy of fresh faces trying to one-up the OG chrome finish, each vying for the crown in either cost-saving or performance-boosting departments. These days, laying hands on a chrome BCG might be akin to a wild goose chase, but boy, is it a feather in your cap when you snag one.


  • Hard-wearing and scoffs at corrosion
  • A breeze to clean


  • Your wallet might feel the pinch more than with other finishes


Fast-forward to modern mil spec mandates, and it’s phosphate that’s stealing the spotlight for military rifles (think M16s and M4s). It’s got an ace up its sleeve over chrome with those cost-cutting perks, plus it flies under the radar with a less glitzy presence out in the field.

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Your no-nonsense phosphate BCGs, assuming they’re crafted up to snuff, will still come with a chrome lining tucked away inside the gas key and the carrier’s insides where those gas rings do their dance. No dice on that for the other finish options – Nitride, DLC, you name it – they’re left wanting in the chrome-lined department.

Some folks have a soft spot for that gritty phosphate texture, given its knack for cozying up to oil compared to the slicker finishes. Eventually, this roughness smooths out at the typical wear hotspots, like the carrier rails.


  • Gentle on the wallet
  • Steady under duress and thumbs its nose at corrosion
  • Mil-Spec cred


  • The coarse texture is high-maintenance on the lube front
  • Tidying up takes a bit more elbow grease

Black Nitride

Alias alert – Black Nitride, also known under the guises Melonite, Salt Bath Nitride, and good ol’ Nitride. This is where they amp up the heat to give the metal a case-hardened moxie by permeating it with nitrogen. What you get is a hide that’s tough as nails, warding off both wear and tear and corrosion. Plus, it’s as smooth as silk for slick operations and tidying up’s a snap.

Since nitrided bolt carrier groups can skip the chrome lining shenanigans for the gas key and the bolt carrier’s innards, the production purse strings get a bit of a break. And, let’s not overlook the killer curb appeal of Black Nitride’s BCGs, with their snazzy jet-black vibe.


  • Puts up a good fight in the durability and anti-corrosion ring
  • Slick finish that’s low-key on the lube
  • Makes clean-up duties less of a headache compared to Phosphate


  • Might have you reaching deeper into your pockets than Phosphate would

Comparisons are the bread and butter when you’re weighing your options. So take this trove of info and square off the contenders based on what sings to your sensibilities – whether it’s putting fewer dents in your budget, banking on a lower-maintenance steed, or perhaps you’re in it to win it with an aesthetic that pleases the eye.

Black Nitride vs. Phosphate

Black Nitride as opposed to Phosphate—it’s a discussion that’s likely to engage enthusiasts in quite the dialogue. Both contenders enter the ring as relatively economical finish selections. On one hand, Nitride claims superiority in its sheer slickness and robustness.

Minimal lubrication demands and a reputation for simplistic cleansing routines underscore its practical appeal. However, despite its merits, Nitride’s absence from the mil-spec echelon for Bolt Carrier Groups (BCGs) presents a sticking point for purists.

Conversely, Phosphate converses with the past, its tenure of dependable service to the military is noteworthy, and its utility stands beyond reproach. For those steeped in tradition, the tactile satisfaction of Phosphate on their BCG can’t be dismissed.

Two routes diverged in a wood—both lead to satisfactory destinations. But through the lens of sheer performance, Nitride seizes the laurels. Yet, when the heart yearns for the resonant echoes of yesteryear, Phosphate’s victory is written in the stars.

Black Nitride vs. Chrome

Transitioning to the exoneration of Black Nitride versus Chrome—each a titan in its own regard, these surfaces whip contention into a frenzy. Both are hardened warriors of cleanliness, unyielding in the face of adversity, ever-ready to withstand the rigors of duty and rebound with vigor. A Chrome BCG, however, is that elusive beast, challenging to procure, and demanding a premium upon capture. 

Opting for Chrome may be driven by aesthetics—the allure of its hue, the singularity of its shine. Maybe it’s the siren call of a retro homage that reels you in—commendable! For Chrome bears an eternal allure, an opulence that doesn’t necessitate rational justification.

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Yet, should you find intrigue in preserving functionality while pocketing a few extra bills, Nitride stands undaunted—a sage choice indeed!

Nickel Boron

Nickel Boron, a state-of-the-art metal finishing contender, steps up to the plate with a robust resistance profile against wear and corrosion, not to mention it slides into the mix with an exceptionally low friction factor. When you pop the hood on a nickel boron bolt carrier group, you’re looking at superior lubricity and anti-corrosive properties that outshine its peers in chrome and nitride BCGs. It’s no shocker, then, that it’s snagged the popularity vote in the AR-15 BCG finish elections.

Planted firmly in Palm City, Florida, UCT Coatings flaunts their proprietary EXO Nickel Boron finish – a finish so slick it’s grabbed the MIL-SPEC badge for select Army mortar tube parts. It’s not just a coat; it’s armor.

Let’s hash out the pros and cons:


  • Smooth operator slickness
  • Hardcore durability
  • Stellar corrosion defiance


  • A few more greens than some other finishes out there

Nickel Boron vs. Nitride

Striding confidently beyond phosphate in the departments of slickness and cleaning convenience, Nickel Boron takes the lead. Sure, there’s a price tag to consider – it usually stands a few dollars above Nitride. But the question lingers: does that subtle uptick in performance echo your name? If you’re nodding, wallet in hand, captivated by its luster, then it’s a Nickel Boron headliner for your day. Otherwise, if you’re shrugging off the glitter, grab some Black Nitride and call it a day!

Nickel Boron vs. Chrome

Step right up to witness the clash of the metallic titans. Tradition clashes with innovation. Hard Chrome muscles out in hardness, but Nickel Boron glides by with unrivaled slickness. Each contends with their own brand of distinction, wielding their unique allure. If you gravitate towards that extra gleam, Nickel Boron’s got you covered with its reflective charisma compared to Chrome’s understated vibe.

Hunting down Chrome might lead to some rummaging and a heavier purse, while Nickel Boron is just a stone’s throw away. It’s a tie; choose your champion based on the visual punch you’re aiming to pack.

Titanium Nitride

Titanium Nitride stakes its claim as an exceptionally tough ceramic substance, commonly enlisted in aerospace and military spheres to enhance the ease of maintenance, the simplicity of cleansing routines, and the persistence of a sharp edge. 

This coating boasts a superb combo of slipperiness, rock-like hardness, and stalwart resistance to corrosion. Sure, you might stumble upon these perks in other finishes. However, the real draw for choosing this one is arguably aesthetic. That singular gold hue delivers a striking juxtaposition against the understated matte black of an AR-15. 


  • Gleams with a seamless, rugged, and slippery surface.
  • Flaunts an opulent, gold-plated aesthetic.


  • Your wallet might feel a pinch.

Surveying the landscape of potential finishes for AR-15 BCGs, it’s clear the possibilities reach as high as the heavens. Every finish touched upon here comes with the mark of quality, and a solid BCG will serve its purpose adequately irrespective of the chosen finish. Essentially, the finish that ends up adorning your equipment boils down to whichever one strikes your fancy.

The market teems with options, yet to cut a long story short, it’s pretty darn difficult to go astray with the classic phosphate-finished BCGs. Should you hanker for a version that’s a breeze to clean and boasts smoother surfaces, the Nitride, Nickel Boron, and DLC finishes are also commendable for their durability and slickness.

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