The BCG is of course your Bolt Carrier Group, without one you have a very nice looking tube, and it affects everything from accuracy to recoil. You can change the entire feel of your AR by a bit of modification of the BCG for instance you can turn your rifle into a grenade. If you are looking for the Best BCG you want to look for a standard, milspec BCG with a premium coating, much else and you will affect the performance. A lightweight BCG with no other changes to the rifle will increase felt recoil and wear quickly, while a gimmick BCG can turn your rifle into a small IED. It is better to change nearly any other system in the rifle than the BCG for performance because of the headspace between the bolt and the rifle barrel. Most failures to fire come at the point of the BCG due to any number of problems, while the BCG might not be the cause of the problem; usually it is gas system or magazine related. One of your first steps is to remove the BCG to perform maintains on the rifle.
If you want a high speed, low drag AR-15 with no recoil; that you can mag dump into 3 gun targets as you are hiking through the woods shouting, “Wolverines!!!”, that you never need to clean and will last a lifetime at a low price, we have what you are looking for. Just step this way, to my Nigerian friend, he is a bit down on his luck and could use some help to transfers his remaining BCGs out of Nigeria but you will be paid back double, but now I would like to talk to you about your 1993 Dodge Darts, extended warranty, and have you hear about this new bitcoin, I’d love to sell you, cash only and in small bills please.
- What is a BCG
- Why Do You Need a BCG?
- Best Bolt Carrier Groups
- Amazing Bolts That Didn’t Make The Cut
What is a BCG
The Bolt Carrier Group is made up of the carrier, gas key, firing pin, bolt and extractor. Each of these parts can be replaced within a BCG to give better performance, but most people will be fine with a standard bolt, higher quality parts improve function and reliability but fit is standardized, and spending money to improve accuracy is better saved for the barrel, as long on the locking lugs are to spec.
Remember friends don’t let friends use unstacked gas keys.
Full Auto bolts are made to mil-spec meaning that they can be used in nearly any AR-15 rifle and if you someday find the gods smiled on you and are able to register an AR-15 as a full-auto rifle you can shoot full auto. Never buy anything but a full auto bolt. There is just no reason not to, but more importantly the semi-auto bolts give no advantages. None. They are relics of a dark time period.
Forward Assist Notches
There was a time not so long ago that AR-15s didn’t have a forward assist on civilian rifles because the lack of knowledge when you smack the forward assist. Thankfully that time is gone and unless you are buying an upper without forward assist you will want to be able to use the forward assist to push the rifle into battery. Most BCGs come with FA but some don’t as a relic of the old days.
Lewis Machine Tools uses a dual spring extractor, LMT is considered one of the best gun manufacturers in the world, if you want to increase the extraction of your rifle grab the kit off the LMT website but otherwise most AR-15s will extract fine.
Coatings are a hotly debated subject within the firearm community unless you are not cleaning your rifle or you are firing 1000s of round per session. You don’t need to spend more on a fancy coating, most rifles will function perfectly for some time without being cleaned more than once a year but the right coating does make it easier but the cost is more. Whether the cost is worth it is up for debate.
Melonite or Nitride bath is the most common coating; it is easy and works well for most users. If you hate cleaning your rifle with a passion opt for Nickel Boron. The other coatings and there are many, fall between price and ease of use. Unless you are building a $3000 rifle-to-run competition there isn’t much reason to go crazy with the coating. Pop the BCG out after a session at the range and wipe it off with a rag before you head home. When you clean your rifle for the season pay a bit more attention to it.
Why Do You Need a BCG?
You may think this integral part comes with every gun but many of the best deals on uppers come without a BCG or charging handle included, because as the mitochondria of the gun it does most of the work. Their relatively low cost means anytime you update your barrel or upper it should have its own BCG, this will keep your headspace in spec compared to a worn-down BCG and barrel combination. Headspace is the most important factor you can control; it locks the bullet within the battery to fire. An improper headspace with causes the round to direct the firing not completely into the barrel. This may not be a problem immediately but if you have seen a rifle blow up in the hands of an operator it is because the headspace became weak and lost its integrity.
Luckily nearly all bolts are made to mil-spec allowing thousands of rounds to be fired without concern.
Best Bolt Carrier Groups
PSA – The best Deal
PSA’s Nitride MPI Full-Auto has everything you want, as well as a bonus of 10 Magpul 30 round magazines. The nitride carrier is easy to clean and reliable. Gas keys are staked, and it is Magnetic Particle inspected to remove tiny metal shaving that could harm your receiver and stop function. It is bare bones but it is the best deal and shoots great. Not to mention you won’t need to buy any magazines for a while. Perfect for a new build or a barrel swap.
The PSA is made from 8620 steel with a bolt made from 9310, Gas keys staked to mil-spec and the Nitride finish still looks pristine after nearly 2000 rounds. The PSA is the best buy because of the P-Mags from Magpul they are what everyone should use for their first sets of magazines with only Lancer being preferred over Magpul for a set of forever magazines.
Just before publishing this article, I found a Brownells having the same deal on their site. I think they both are great BCGs but I love Brownells customer Service. Go with Brownells if you get the choice.
BCM – The high end
Brave Company is a great producer of AR-15 rifles and parts. They do everything PSA does but with a bit better quality. You may need a microscope to see the different wear but BCM parts will almost universally last longer and function better due to increased quality control and machining tolerances.
So what is the actual difference? BCM has smoother finish, less tool marks, and probably a more reliable part. PSA may run two CNC passes while BCM runs three. Should you pay for the difference? Probably not, unless you have experienced a failure on a hunting trip or when you can’t find parts, you will not understand why I am recommending the BCM; if you have you will already be sold on the BCM and won’t be using cheaper parts anywhere on your rifle anyway.
Aero Precision – The hero of the common man
Aero Precision is the in between BCG higher quality than the PSA or Toolcraft, but less than the BCM, I recommend the Nickel Finish unless you feel the need to have a black BCG. The quality of Aero Precision is always superb but they are difficult to find because they are the current sweet spot between price and quality. Aero Precision is the best of the middle, they are the company that sets the standard for the average because if you can’t beat them on price you better beat them on quality, and both are dam hard to do.
The Aero Precision is of course made from 8620 steel, the bolt is 158 tool steel, Magnetic Particle inspected, gas key staked and the Black Nitride is very slick even after a thousand rounds. Aero Precision has been the champion of the “Budget Builds” for years and in 2021 it is no different.
Brownells – Eat Karens for Breakfast
Brownells is another great BCG; they are a bit more expensive than PSA or Aero Precision, while being nearly identical for one reason. Brownells has probably the best customer service in the industry. The company out of Iowa, yeah, I might be a bit bias, but let me refer you to their Customer Service FAQ for my reason to recommend them.
How long do I have to return an item?
This is why I always recommend them for all firearm related purchases. If possible buy from Brownells, if they can’t help you, no one can.
Brownell’s products are high quality with a great finish and smooth operation. Black Nitride, HPMI. The gas keys are properly staked, and the materials feel high quality. The great deal is again you get 10 magazines along with a great bolt.
Toolcraft – The budget pick
Toolcraft is the reason I don’t have much to say about the difference in BCGs between PSA, Brownells and Aero Precision, now I can’t confirm it but I strongly believe that Toolcraft makes them all. Toolcraft bolts are great bang for the buck. The Toolcraft bolt has few tool marks and a great polish. Staked gas keys and solid lockup in the rifle. Toolcraft BCGs are known to fail after 15,000 rounds. Yes, there have been a couple of known failures at the 15,000 round mark. For those of you that don’t know 15,000 rounds is a massive amount for a gun, more than most people will shoot in their life. If that is a worry make sure you grab a BCM, or JP Enterprises.
Amazing Bolts That Didn’t Make The Cut
The problem with BCGs is that everyone from Adaptive Arms to Zebra rifles makes a BCG, even Surefire, famous for their light accessories, make BCGs. So a huge number of Mil-Spec BCGs are available, since the technical data is available. Mil-Spec Bolts mean that it will fire a minimum of 6000 rounds and is interchangeable on the M4 or AR-15 platform. Some of the BCGs I would love to recommend but won’t because the price. The increase in price gives you nothing over the BCM BCG but you make like a company because you had a great experience with them. If so leave a comment on the BCG below.
CMMG – The 22LR Adapter
CMMG makes one of the best training tools for an AR-15, the ability to shoot 22lr rounds. 22lr rounds are usually so cheap you don’t care how many you fire. They are great for learning trigger control, left and right hand shooting, offhand shooting, positioning, run and gun, rapid fire and windage. Using 22Lr rounds to practice has been a concept since World War 2 when soldiers would train with 22LR M1 Garand, Springfields, and Carbines to save ammunition as production was ramped up. Shooting 22LR is great for winter practice since many indoor ranges will not allow you to fire full power rifles indoors.
The CMMG is a quick and easy swap of the BCG and magazine; you can go from training to use in minutes. This is my favorite tool for new shooters because it allows them to practice grips, and sight picture while spending 1/5 the money. That means more rounds and range time, which means more fun.
The downside to the CMMG 22lr adapter is that it will run dirty because of the rimfire round. This is great for kids because it teaches them how to clean a truly dirty rifle. Even if you don’t want to use your competition rifle to shoot 22lr it is a great tool in any situation, allowing you the peace of mind from the two most plentiful ammunition types.
Otis B.O.N.E. Tool
The B.O.N.E Tool makes cleaning AR-15 BCGs simple and easy, it reaches into the crevices of the BCG to remove that baked on crud that sucks to clean. The B.O.N.E. tool cleans the BCG, Bolt and Firing Pin. It also works very well as a cleaning rod handle to give you more leverage to scrub the bolt.
Andrew Maurer is a Precision Rifle Series competition shooter and gunsmith. Building competition rifles for over 12 years. He works as a big game hunting guide in Iowa, South Dakota and Arizona. He is also a political scientist studying the effects of gun control on society. He teaches youth rifle shooting.