Featured Best AR-15 Bolt Carrier Groups (BCGs) [2023 Buyer’s Guide] David Lane October 7, 2022 Join the Conversation BOLT CARRIER GROUPS ARE WHERE THE RUBBER MEETS THE ROAD 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. Sionics Phosphate BCG 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. Nitride BCG 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. KE Arms Chrome BCG 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. Cryptic Coating BCG 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. NP3 is also great on fire control groups 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. Brownells TiN BCG 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. Carpenter 158 bolt 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. Toolcraft Phosphate BCG 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. Daniel Defense Phosphate BCG Downside? MSRP is $221. And the street price is… $221. Oof. 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. Palmetto State Armory Nitride BCG If cheap is what you need, this sells for about $70. There are some corners cut with this BCG, like no chrome lining, 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. Palmetto State Armory Nitride BCG Maybe spring for a true Mil-Spec bolt for a home defense gun, but for a range plinking budget rifle, this fits the bill. 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. Cryptic Coatings DLC BCG 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. Technically made by Young Manufacturing, KE Arms bought YM not too long ago and have brought the operation in-house. KE Arms Chrome BCG 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. Bootleg Adjustable BCG A more outside-of-the-box design than most, Bootleg’s BCG is adjustable. Basically, you can tune the gas right at the BCG instead of having to do it elsewhere in the system. This is really nice for shooting suppressed, but is otherwise a bit much. The BCG is made from S7 Tool Steel and is lithium isonite coated. This is a niche BCG for niche applications, but for those of you that want to dedicate a BCG to shooting suppressed – this is pretty awesome. Bootleg Adjustable BCG MSRP is $200. Rubber City Armory Titanium BCG As a general rule, I really don’t recommend titanium or low-mass BCGs. Mass in a BCG is good, and there are other places in the rifle to shed weight. That said, if you want a low-mass BCG – this is the one to get. Rubber City Armory Titanium BCG For the ultimate race rifle, a Titanium BCG cuts a lot of weight out of the BCG while keeping it very strong. Rubber City Armory is the best of the best in the world of low-mass and makes one hell of a durable BCG. This one features a 9310-steel bolt and tool steel for the extractor and cam pin. MSRP is $360. 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, BetterGuide To Super-Light AR-15 Bolt Carrier GroupsFirst Impressions – GEMTECH Suppressor Bolt Carrier Explore RECOILweb:New Metal FOMI Style Clip From Discreet Carry ConceptsNew Speer 10mm Gold Dot Defense LoadThe Danger Zone Auction: LOTS of Loot AvailableSARA: Sordin Arc Rail Adapter NEXT STEP: Download Your Free Target Pack from RECOILFor years, RECOIL magazine has treated its readers to a full-size (sometimes full color!) shooting target tucked into each big issue. Now we've compiled over 50 of our most popular targets into this one digital PDF download. From handgun drills to AR-15 practice, these 50+ targets have you covered. Print off as many as you like (ammo not included). Get your pack of 50 Print-at-Home targets when you subscribe to the RECOIL email newsletter. 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