Best Bolt Carrier Groups and Metallic Coatings – A Comprehensive Guide

What Does This Guide Offer?

Well, if you are on the lookout for some information on different kinds of best bolt carrier groups and coatings on the internet, you might not be able find all of it at one place. Even if you manage to find some information, most of it might be too technical to understand, especially, for amateurs.

​Each BCG comes with its own merits as well as demerits, while some have none! It all depends on the user and the purpose. In this guide we will discuss about the various kinds of bolt carrier groups and some prominent coating methods and their effect on BCG’s so that you can make an informed decision on which BCG to choose and what kind of coating can serve your purpose. Shall we begin?

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​Bolt Carrier Group, Why Use It?

Any best bolt carrier group (BCG) is the most essential part of a rifle. We all know that any sort of equipment needs maintenance. The only difference is, some need maintenance very frequently, may be sometimes daily, while others need maintenance at regular intervals.

​Just like any other equipment, your personal firearm(s) also needs regular maintenance and thus the need for an appropriate bolt carrier group. They help your gun perform to its optimum as it was intended to and at the same time reduce the maintenance frequency and costs. And this is the exact reason why most gun owners keep upgrading their ammo with state of the art BCG’s which not only increase the performance of the firearm but also increase its durability.

​Bolt carriers enhance your gun’s performance by reducing the friction, lowering the operating temperatures and help your ammo to perform at its best irrespective of the weather and climatic conditions. Now let us have a look at various types of BCG’s and BCG metal coatings.

Types of BCG’s and Coatings

Let us first start with BCG’s. Essentially, as the name suggests, bolt carrier group carries the bolt of the rifle and directs it within the range of the receiver. It also helps in resetting the hammer after each round. Following are the various types of bolt carrier groups available in the market:

1. Types of Bolt Carrier Groups

  • AR-15 Bolt Carriers Group:

The AR-15 is a semi-auto bolt carrier. In this type of carriers, the cutout at the bottom is a bit large compared to other types of bolt carriers and is designed in full circle. This extra large cutout helps reduce the overall weight of the rifle as preferred by some users. However, there is no major difference between the bolts used by AR-15 and other carriers. However, AR-15 Bolt Carriers are much cheaper compared to M-16 Bolt Carriers.

  • M-16 Bolt Carriers Group

M-16 is a fully-automatic bolt carrier. It has a shorter but a fuller diameter section towards its rear end which increases its weight by one ounce. Though a bit heavier, these types of carriers are much more stable than AR-15 BCG and are loved by all those gun enthusiasts who want their rifle to be fully automatic.

  • Mil-Spec Bolt Carrier Group

These types of bolt carriers are manufactured following the standards specified by the US Military. For a bolt carrier to get qualified as a Mil-Spec BCG, it has to meet the following standards:

(i) It should be made of Carpenter No. 158 steel

(ii) Interiors should be Chrome plated

(iii) It has to undergo shot peening process which increases the metal fatigue life

(iv) The fasteners used in these bolt carriers should be made from Grade 8 carbon-alloy steel, the toughest of the fasteners

  • Half Circle Bolt carrier Group

Unlike AR-15 carriers that have a full circled end in the rear, half circle carriers have a semi-circle rear end, just as the name suggests. In order achieve this design; the rear circular end is milled of along with the “shroud (the area located at the back under the firing pin). This makes Half Circle Bolt Carriers even lighter than AR-15’s, making it much easier to use, especially, for amateurs.

  • Low Mass Light Weight Bolt Carrier Group

This carrier is the lightest of all the BCG’s. As a result of its ultra low-weight, the recoiling force is considerably lessened during firing. This helps the user to fire shots rapidly in a quick succession too. This is the reason why most users operating in a 3-gun environment prefer to use low mass low weight BCG. Having said that, I should make you guys aware that the low mass of these carriers quickens the wear and tear, and as a result this type of BCG cannot work as a long-term solution for your rifle.

2. Most Prominent Metal Bolt Carrier Coatings

There are a whole lot of coatings available for various kinds of BCG’s depending on their working environments. These metal coatings offer resistance against corrosion, pitting and chemical degradation. The most commonly used best bolt carrier group coatings are:

  • Nickel Boron Bolt Carrier Coating

Nickel Boron coating can be applied to the BCG’s by a process known as electroless plating. This helps in resisting corrosion and lubricates the BCG which in turn makes for an easy clean-up. Apart from that, this coating gives your BCG a sophisticated metallic-silvery look.

  • Phosphate Bolt Carrier Coating

Phosphate coating can be applied to your BCG by drowning it in hot phosphoric acidic solution. This process is also known as Phosphating or Parkerizing. Phosphate coating helps increase the overall thickness of the BCG providing it a greater durability. The wear and tear factors are also considerably reduced. The coating gives your BCG a sleeky medium-greyish look. Special Phoshating can result in black metallic coating for maximum concealment of your weapon.


Whichever BCG you choose, keep in mind that the testing of the bolt carrier is the most important factor, as it governs the quality and performance of the carrier. To ensure that you are buying only the best bolt carrier group, please check if the BCG is magnetic particle inspected (MPI) and if it has gone high pressure testing (HPT). This way you can check if the BCG has any cracks on its surface and whether it is durable enough or not.

Also, please perform some groundwork before you jump into a decision. Confirm to see if the manufacturer performs batch check or individual check. If the BCG comes with a batch check, its better you look for another option. Most of the reputable bolt carrier group manufacturers perform individual checks and this would be a safe bet for the kind of money you are investing. Also, make sure that the bolts attached to the gas key are staked in their proper place to prevent any loosening due to the pressure exerted while firing. Now that you have some firsthand information on best bolt carrier group and metal coatings, I hope your shopping will be a fruitful one. Thank you!

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