BEST BOLT CARRIER GROUPS

• Basic Just Works: Toolcraft Phosphate BCG
• Basic Filling With A Fancy Name: Daniel Defense Phosphate BCG
• Sex Appeal Matters: Wilson Combat
• On A Budget: Palmetto State Armory Nitride BCG
• Great Value Option: Lead & Steel ARC BCG
• Editor's Pick: Cryptic Coatings DLC BCG
• Best Chrome: KE Arms Chrome BCG
• Pick Your Weight: Young Manufacturing Variable Mass Carrier
• Small Batch Perfection: Walker Defense Research FDE DLC

While most people will say that the BCG is the heart of your rifle, most people don’t know why or what makes a BCG good.

We’ll break it down for you, so you know exactly what you’re getting into. We also have some great recommendations for BCGs to get you started!

WHY YOUR BCG IS IMPORTANT

If you’re not familiar with AR-15s, the BCG is basically the engine that does all of the mechanical actions to make the thing work. 

Stripping a round from the magazine, pushing that round into the chamber, keeping the firing pin safe, letting the firing pin forward, keeping the pressure in the chamber long enough for the bullet to leave the barrel, extracting the case, ejecting it, and finally stripping a new cartridge from the magazine.

All the while, the BCG is heating up, cooling down, accelerating at 400 g’s, decelerating to a complete stop, and doing this dozens, hundreds, even tens of thousands of times.

Simply put, the single most important part of your AR-15 in terms of reliability is your bolt carrier group.

If you’re building a new rifle, the two most important parts to not cheap out on are the BCG and barrel. If you’re shooting a factory-built rifle, the biggest potential upgrade you can make for a long lasting, durable rifle is a new BCG.

FULL-AUTO VS. SEMI-AUTO BCG

There are a couple of names for these, but the bottom line is there are two types of BCGs for the AR-15/M16. “Full-auto” or “M16” BCGs and “semi-auto” or “AR-15” BCGs.

Basically, the full-auto/M16 type of BCG has a slightly larger backend to the BCG so that it can engage with a full-auto trigger sear in a full-auto lower.

The semi-auto/AR-15 BCG has a smaller backend and can’t.

Unless you own a full-auto firearm with a third pin drilled and a full-auto trigger installed, it doesn’t matter what kind of BCG you use. Both BCG types are entirely legal. A full-auto BCG alone cannot make your rifle full-auto, and you are in no legal hot water owning and using one.

That said, the semi-auto/AR-15 style BCG doesn’t really offer anything better or different except that it can’t fire in full-auto when paired with a full-auto lower.

This is something you can ignore unless you’re in the <1% who happened to throw down a crapload of money on a full-auto lower. For the rest of us 99.9%-ers, it won’t matter what kind of BCG you get. Most of them are full-auto/M16 style simply because it’s “Mil-Spec” and has become the standard.

Hyper-technically speaking, full-auto/M16 style BCGs are also generally a little heavier and are probably more reliable because of it. This really depends on who makes it and to what exact specs and isn’t really enough weight to matter much either way.

COATINGS

One of the biggest innovation points in the BCG world is the coating applied to the outside and inside of the BCG. The Mil-Spec default is phosphate. Tens of millions of ARs have collectively shot billions of rounds using phosphate BCGs, but that doesn’t mean that it can’t be improved on.

Some coatings are snake oil and are just there to make things more expensive; some actually provide a real benefit. I’m not a material scientist, but I’ll do my best to give you a rundown on the popular options.

Parkerized (Phosphate)

The OG and the Mil-Spec, phosphate is the most common and normally cheapest coating that you will find. It works, it works well. Millions of rifles have gone into combat with phosphate BCGs, and America still stands.

That said, MILSPEC is also the lowest acceptable standard. While phosphate is good enough and super durable, it’s a very rough finish that requires more effort to clean, more lube to keep running, and is generally ugly.

Nothing wrong with ugly on a working rifle, but it’s something to mention. 

Black Nitride

Second in popularity only to phosphate, black nitride is a cheap and easy-to-apply coating that works wonders.

A chemical process that diffuses nitrogen into the first few microns of the surface metal, nitride is a simple process that can be done in bulk and done well.

This makes it pretty cheap to manufacture and gives you a great finish.

It’s smoother and better than phosphate, but it isn’t MILSPEC.

Hard Chrome

This is what MILSPEC should have been if Eugene Stoner had had his way. Sadly, the chrome finishes of the 1960s were not up to par, and hard chrome BCGs had major flaking problems.

With time, technology, and advancements in machining, these problems have (mostly) gone away.

Hard chrome is still a difficult finish to apply to a BCG, but there are more than a couple of brands that have solved the mystery and produce a really great chrome BCG.

Chrome is awesome because it’s easy to clean, requires very little lube, and is crazy durable.

Downside? It’s much more expensive than some other options. Hard chroming a BCG is still not a small task, so you’re limited to very few companies that can do it right.

Diamond Like Carbon (DLC)

DLC coatings are cutting edge in the finish world. Applied through Physical Vapor Deposition (PVD), the end resulting DLC coating is my favorite for BCGs.

DLC is (probably) the strongest and hardest to damage coating available for BCGs; it is also super slick and super smooth, giving a BCG incredible properties. While I don’t recommend it, I’ve actually shot my AR with a DLC BCG for over 3,000 rounds with no additional lube just because I could.

But there is a catch, DLC is expensive and hard to do. Your options for BCGs are limited, and you’ll pay more for them. That said, you get an amazing BCG when you do.

Nickle Boron

Strong, slick, and more expensive than phosphate. Starting to see a trend yet?

Nickel Boron is a great finish and beats many of the competition, hands down. It isn’t as slick or as strong as some options, but it’s a really nice middle-of-the-road. 

Something I like about Nickle Boron is that it comes out as a shiny, dull gray color. While it isn’t chrome, it looks close enough to pass on a not-perfect clone rifle.

Electroless Nickel PTFE (NP3)

The science behind NP3 is a little complex, but basically, this coating is insanely smooth, strong, corrosion resistant, and self-lubricating. 

That self-lubrication comes from the PTFE that is used in the coating. If you slept through science class, PTFE is Polytetrafluoroethylene – or more commonly known as Teflon. 

Be it for fishing nets or making your pans non-stick, Teflon has a lot of uses.

As the NP3 coating wears on a BCG, more and new Teflon is exposed. This keeps your BCG super slick no matter what.

Two downsides, NP3 isn’t cheap, and the production of polytetrafluoroethylene is undisputably pretty bad for the environment. If you want to go a little green, maybe skip the NP3.

Titanium Nitride (TiN)

Another coating that is applied via PVD, Titanium-Nitride is a very cool coating with some great applications. But if we’re being honest, the biggest selling point is that TiN BCGs just look damn good.

Resulting in a bright gold color TiN BCGs look awesome and run great. Very smooth, very durable, and very easy to clean.

While much easier to apply than some other coatings, TiN tends to be a little expensive due to the PVD application and how fancy the BCGs look at the end.

While miles slicker and more durable than something like phosphate, TiN still falls a little short of DLC or NP3+ for slickness.

BOLT MATERIALS: CARPENTER 158 Vs 9310-STEEL

Another place different manufacturers try to stand out is what kind of steel they choose for their bolts. The most common is Carpenter 158 or C-158 steel, and the second most popular is 9310 steel.

The exact difference between them is a lot of scientific talk but the easy version is that 9310-steel is about 7% stronger than C-158 when heat treated correctly. However, C-158 is Mil-Spec.

Why is C-138 Mil-Spec if there is something better out there? Because that’s what the military chose, and they don’t like change.

One small problem with 9310-steel bolts is that they MUST be heat treated correctly to be stronger than C-138 bolts. This is where good quality control comes into play and why I really recommend not going cheap on your BCG.

That said, will it really matter to you what steel is used for your bolt? Maybe, maybe not. As with anything, your use case should lead your choices. If this is a range day plinker BCG, maybe save some money and go Mil-Spec.

If this is the last rifle you will ever own, go big or go home.

I would note that bolts are consumable. They take a huge amount of abuse while firing, and they will wear out eventually. Depending on your ammo, rate of fire, and gas system, a good AR-15 bolt might last between 10,000 and 30,000 rounds. 

Personally, I change bolts when I change barrels and (so far) have never had a bolt catastrophically fail.

MAGNETIC PARTICLE INSPECTED & HIGH PRESSURE TESTED

Bottom line, these are two major quality control checks that ensure you get a good BCG. The best kind is for your carrier and bolt to both be individually MPI and HP tested.

Most manufacturers use batch testing to keep down costs, which means some parts will slip through the cracks. Individually testing each bolt and carrier gives you a much higher degree of assurance that your bolt and carrier and good to go.

BEST AR-15 BOLT CARRIER GROUPS (BCG)

Toolcraft Phosphate BCG

Basic like calcium carbonate, the Toolcraft phosphate BCG isn’t fancy. It isn’t special. It won’t turn heads, and you won’t break Instagram with it. But it works, it works well, and it’s cheap.

Toolcraft has built a great name for itself as a consistently great source for BCGs. In many ways, they are the gold standard for value, quality, and durability that all others are measured against. 

This is a very Mil-Spec BCG that won’t win beauty awards, but it runs. Mil-Spec Carpenter 158 bolt, chrome lined carrier, chrome lined gas key made to USGI specs, and a staked gas key.

MSRP is only $150, but you’ll almost always find these for about $99.

Daniel Defense Phosphate BCG

An aggressively Mil-Spec BCG made by a company with a long history of providing parts to militaries worldwide, Daniel Defense is a premium brand with a premium price.

Heavy phosphate coating, chrome lined, Carpenter 158 bolt, high pressure, and MPI tested, this BCG covers all of the bases and is absolutely a BCG you can trust.

Downside? MSRP is $221. And the street price is… $221. Not the highest on the list but a bit oof for phosphate.

If I had to go to war with a BCG, I would trust DD over Toolcraft. But for most normal applications, I think you can do better for the money.

That said, if you want the best Mil-Spec BCG available – this is it.

Wilson Combat

Really known for their work with the 1911; Wilson Combat is always pretty high on my list for anything they make. From Beretta upgrades to SIG to ARs, if Wilson Combat offers a product for it — it's guaranteed to be good. And it's guaranteed to be sexy.

While bolt carrier groups aren't really a part that needs a lot of drip, WC still manages to make their BCGs just look better no matter what. They're also rock solid and crazy reliable.

Offered in a wide range of flavors from nitride to nickel boron, 5.56 NATO to 458 SOCOM, every WC BCG is built like a tank.

My favorite is their “Bullet Proof” Nitride. The nitride is what you expect, but the “Bullet Proof” is basically an extended warranty that means if you don't like anything, for any reason, Wilson Combat will repair or replace it.

Palmetto State Armory Nitride BCG

If cheap is what you need, this sells for about $70.

This is pretty bare-bones and excludes any fancy features like chrome lining or individual inspection, but the bolt is 9310-steel and magnetic particle inspected. This honestly covers the vast majority of users and will be good enough for most applications.

Maybe spring for a true Mil-Spec bolt for a home defense gun, but for a range-plinking budget rifle, this fits the bill. Personally, I recommend spending the extra $20 and getting Toolcraft mil-spec.

MSRP is $130 but they are almost always “on sale” for $70

Lead & Steel ARC BCG

For a huge amount of value packed into one BCG, the Lead and Steel All-Rounder Carbine BCG is hard to beat — especially at the current price way below MSRP.

Featured in the L&S ARC rifle, the ARC BCG has DLC or TiN coating and is individually proof tested and mag particle inspected. L&S also lays claim to using a tighter tolerance to account for their coating.

A shot-peened Crucible Carpenter 158 bolt that is again individually proof tested and a chrome-lined gas key gives you incredible longevity.

And if that wasn't enough, L&S uses gasket sealant, thread locker, 53 in/lbs of torque, and staking to affix the key to the BCG body. Just to finish it off, this BCG even has a Sprinco 5 coil extractor spring.

The bottom line is that Lead & Steel is covering all of the bases for one hell of a good BCG and doing it at an insanely good price. I've been loving this BCG in the L&S ARC rifle and can strongly recommend it.

MSRP is $330, on sale at the time of writing for $180

Cryptic Coatings DLC BCG

This is my favorite BCG and the style I’ll take over anything else. Years ago, Cryptic Coating sent me a BCG for review, and it’s been kicking ass ever since.

I don’t know how many rounds through mine I have, but it’s got to be past 10,000 by now.

The DLC coating is crazy smooth and slick. I rarely need to re-lube the BCG, and cleaning it can be done with just a paper towel.

MSRP of $280 isn’t cheap, but it is entirely worth it for a BCG you plan on running hard and in less than ideal conditions.

Cryptic Coatings chrome lines their carrier, and the gas key. They also use carpenter 158 bolts, and tool steel for the extractor with a Viton O-ring.

KE Arms Chrome BCG

If you want hard chrome, KE Arms has you covered. Made by Young Manufacturing but owned by KE Arms, this is one of the most long-lasting and durable BCGs you can find. 

KE Arms/YM also uses a special design for the bolt and cam pin. Their patented design does away with the pass-through cam pin design for a captured design that adds a ton of strength to the area.

Oddly, they do not stake their gas key and stand by the idea that staking is not required for a strong connection. I’ve never heard of their BCG key failing because of the lack of staking, so I’d trust them on that.

MSRP is $300.

Young Manufacturing Variable Mass Carrier

Featuring the same cam pin socket and radiused cam pin design as the KE/YM BCG I just talked about, this is the newest BCG from Young Manufacturing and has yet one more cool feature — adjustable weight.

The rear of this BCG is not only hollowed out, but it comes with four inserts of different weight so you can tune exactly how your rifle shoots via the weight of the BCG.

A standard M16 BCG is 11.328 ounces. The base weight of the Variable Mass Carrier is 10.912 ounces. Through the power of the adjustable weights, you can tweak your BCG to be between 11.5 and 13.3 ounces.

• Weight 1: 0.722, 11.552oz total
• Weight 2: 0.738, 11.808oz total
• Weight 3: 0.780, 12.48oz total
• Weight 4: 0.832, 13.312oz total

Why? To adjust how your rifle performs. Suppressors, gas systems, different barrel gas ports, the weight of the buffer, the strength of the recoil spring, and the ammo you use will all affect how your rifle runs. How smooth the recoil is, how reliable the feeding is, everything. An adjustable BCG gives you one more point of change to tweak the overall system.

Will this feature change your life? Probably not, but it is a clever way of adding adjustability without compromising reliability. If you want to really dial in your rifle, I really like this system.

MSRP is $280 for the black BCG and $350 for the hard chrome

Walker Defense Research

What WDR offers more than almost any other brand in the space is hyper-focus on anything they make. This isn't a mega-brand that produces a billion units a year, instead, they are a small set of experts committed to as close to perfection as manufacturing can get./im

The results are pretty awesome. WRD's BCG isn't using some crazy fancy design or a magical coating. And they only come in a few flavors. Titanium bolts for super lightweight builds, FDE color DLC, or Nickel Boron. That's it.

What you get is a BCG that is near perfect. Because these are fairly small batches, the quality control is rigorous, no step is skipped, no corner cut. Every bolt is run through MPI and the gas keys are staked using Optimized Carrier Key Screws.

I've run the FDE DLC BCG through the rain, mud, dust, heat, and cold. It never stops. It just runs. Impressive.

MSRP is $210

LOOSE ROUNDS

The BCG is the most important part of your rifle for durability and reliability. If you really need to cut pennies from your build, you can. But if you want a rifle that will run no matter what, it’s best to spend at lest a couple of bennies on your BCG.

READY FOR MORE?

• AR-15 Upper: Build, Buy, Better
• Guide To Super-Light AR-15 Bolt Carrier Groups
• First Impressions – GEMTECH Suppressor Bolt Carrier

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