While there are many different components that make up an AR-15 rifle, the most important one is easily the bolt carrier group. With Eugene Stoner’s direct impingement design, there is a lot more going on inside the bolt carrier group than with a piston gun, such as an SKS or AK variant rifle. As such, it is very important to consider all the factors and know exactly what to look for when picking out your bolt carrier group. Picking the wrong BCG can be the difference between a rifle that runs flawlessly, or gives you nothing but problems at the range. If you want to learn more about how to pick out the best BCG in 2021 for you, keep reading!
Short On Time? Here Is The Bullet List
- Best Budget Bolt Carrier Group: Toolcraft Premium Nickel-Boron BCG
- Best Premium Bolt Carrier Group: Bravo Company Manufacturing BCG
- Best Cheap Bolt Carrier Group: PSA Nitride BCG
**Below are our more detailed reviews. Click the links above to see current prices or read customer reviews on Amazon.
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What to Look for in A BCG
What is in a Bolt Carrier Group?
As the name implies, the bolt carrier group consists of 2 main parts: the bolt, and the carrier. While these items are almost always sold as a group, it is possible to purchase them separately, but it isn’t very common. While there are some instances where you may want to purchase only a bolt to save a few bucks, it’s usually not a good idea or even feasible for the average builder. For all intents and purposes, the best thing to do is just buy the whole bolt carrier group.
When looking at the plethora of BCG options available, you may notice that a majority of them are advertised as “M16” or “Full Auto” bolt carrier groups. This can add quite a bit of confusion to the selection process, but in reality, it is actually very simple. The only difference between a full auto and semi-auto profile BCG is how the rear of the carrier is cut. You will notice that on a full auto carrier, the rear underside of the carrier will extend out even with the rear topside, while the semi-auto profile is milled further back. On the full-auto profile, this extra portion is what trips the auto sear as the bolt closes and allows the firearm to discharge automatically.
Wait a minute! How can owning a part like this be legal? That’s a great question! Since the only job of the carrier is to trip the auto sear, and it does not actually contain any parts that make the rifle fully automatic, it is perfectly legal to own and use a full auto profile BCG, as the carrier in and of itself will NOT make your rifle fire in full auto. So what does this mean for you? In all reality, not much. The very minor differences between the 2 carriers are going to have very little impact on your overall shooting experience. Typically the full auto profile carriers are more popular, and they are what I stick to with all of my builds.
The world of metallurgy can be incredibly complicated. The number of alloys and heat treatments and other methods of processing steel are almost infinite, and new methods are being developed every day. Thankfully, when it comes to the steels used in AR-15 BCGs, there are only a few different varieties, and picking the best one is pretty easy.
When it comes to the carrier, the quality of steel doesn’t matter that much, so many of those are made of the softer 8620 steel, which is fine. Where it really starts to matter is the bolt. The bolt of the rifle is under tremendous stress, as it has to reliably lock up, and remain locked up under well over 50,000 PSI! Here you have 2 main options: Carpenter 158, and 9310 steel. 9310 is a relatively new player in the market as it is not mil-spec. Some people claim that 9310 can be even better than carpenter 158, but I personally prefer carpenter 158, as it is the mil-spec “gold standard” of bolt materials.
Treatments and Coatings
When it comes to the quality, color, and finish of your finished BCG, you have quite a few options. These options will range from purely cosmetic, to absolutely vital to quality and function. To cover this more in depth, I’m going to break them down in order from most important, to least important.
When picking out a BCG, you will absolutely want one that has been high-pressure tested (HPT), shot peened, and magnetic particle inspected (MPI). These treatments and inspections increase the strength and reliability of your bolt and ensure that you receive a quality end product that has been tested and proven reliable. Forgoing some of these treatments and inspections can help drive down costs and create a lower price, but if quality is something you demand I wouldn’t consider purchasing a BCG without all 3 of these treatments.
Another important treatment is chrome lining of the internal components of the BCG. Since the AR-15 is a direct impingement rifle, a portion of the gas generating by firing the rifle is routed back into the bolt carrier group to cycle the rifle. Since these areas are very hard to clean, it is very important that they are chrome lined to prevent corrosion that may shorten the useful life of your bolt.
Finally, you will want to choose a finish that is both functional and aesthetically pleasing. A few common finishes are nitride, nickel-boron, titanium nitride, and parkerized. Of all these finishes, titanium nitride is going to look the best. The wide range of colors and the intense shine produced by this coating is not only just plain cool, but it adds some functionality as well. The slicker surface is easier to clean and requires less lubrication to run efficiently. The same goes for the nickel-boron finish, however this one is usually only available in a silver color.
This leaves us with nitride, and parkerized. These are 2 pretty common finishes, and it really comes down to personal preference on this one. I feel like my nitride BCGs look a little better and are easier to clean, but my parkerized BCGs are more durable and higher quality. At the end of the day, whatever finish you choose is almost entirely personal preference.
There are a few other minor things to look for when purchasing your BCG. The first is going to be a gas key that is properly staked with grade 8 fasteners. This is actually a pretty major component that is very important, but I consider it to be a minor consideration because I have yet to find a BCG for sale without properly staked grade 8 fasteners. It’s a good thing to keep in the back of your mind, but more than likely any BCG you order is going to include this anyways.
Another thing to consider is the branding or marking on the BCG. In my experience, any BCG that is marked with the companies logo is going to be a higher quality product than a cheaper “generic” or unmarked BCG sold by the same company. In fact, the BCG is about the only component where I have a very fierce brand loyalty to my favorite manufacturer, and it’s for exactly this reason.
Best AR15 Bolt Carrier Group in 2021 Options
Best Budget Bolt Carrier Group:
If you’re on a budget and are looking for a good quality BCG that won’t break the bank but still has all the features you want, then this nickel-boron BCG from toolcraft is the perfect place to start. Toolcraft is notorious for providing equipment that is a step above the basics, while still being priced far less than the premium brands. With a shot peened and MPI carpenter 158 steel bolt, this BCG has all the makings of a premium product, with a budget price. This product also gets bonus points for it’s slick and attractive nickel boron coating, which will be easier to clean and increase your overall reliability. If overall budget is important to you, but you don’t want to buy bottom of the barrel parts, then this BCG from toolcraft could be exactly what you’re looking for.
- Nickel boron coating
- MPI and shot peened bolt
- Not as nice as a premium brand
Best Premium Bolt Carrier Group:
If you’re willing to spend a little extra money for a premium brand, then this BCG from Bravo Company Manufacturing (BCM) is the product to get. I built my very first AR-15 with a few BCM parts, and their quality, value, and customer service have been astounding. In fact, BCM is one of the very few brands that I am incredibly loyal to due to their incredible quality. The BCM bolt carrier group I installed in my first AR-15 is still functioning flawlessly many thousands of rounds later in what is now my 3-gun competition rifle. I truly can’t say enough good things about this company and their products. If you want to build a rifle that you can trust your life to, you should look no further than Bravo Company Manufacturing
- High quality
- All the bells and whistles
- Stellar customer service
Best Cheap Bolt Carrier Group:
If you are on a very strict budget and are trying to build a rifle for as cheap as you possibly can, then it doesn’t get much better than this plain nitride BCG from PSA. It leaves quite a bit to be desired in the features department, as it lacks internal chrome lining, high-pressure treatment, or shot peening. It has been magnetic particle inspected, however, so that is a bit of a bonus, even though the bolt is made out of 9310 steel instead of the mil-spec carpenter 158. Overall, this isn’t too bad of a BCG, and the several that I own run fine, although I usually keep my cheaper rifles at a much lower round count. At about half the price of the other options on the market, this can be a great place to save some money as long as you understand it’s limitations.
- Cheapest option
- MPI bolt
- No HPT or shot peening
- 9310 steel bolt
- No chrome lined internal parts
Best AR 15 Bolt Carrier Group Final Thoughts
When picking out the parts for your next build, each part is going to be just as unique as the rifle they make, and the BCG is no exception. Do you really need a premium BCG for your beater truck gun that only gets shot at the occasional coyote? probably not. But if you are building a high-quality duty or competition rifle where performance is a requirement in any condition, the BCG is absolutely not a place to skimp on. While all the BCGs listed above will be great additions to specific builds, there is one that rises above all others as the absolute best. The fact of the matter is, when my life depends on it, the only one I would put my trust in without a doubt is the BCG from Bravo Company Manufacturing. If absolute quality is what you demand, then you will only be disappointed by anything else.
So now that you have all the information you need, you can go and purchase the best BCG for your next build today!
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