Gunner Quinn
They include:
- CAR (Colt Automatic Rifle): This one used to be the name of a certain group of AR-15s and M-16s back in the 1970s, but today it is a name for carbine-length rifles.
- Light: This one is just what it sounds like, it’s lighter than others but it’s vulnerable to the heat associated with rapid firing. This one’s .625-in in diameter.
- Heavy (Bull): This one is heavier and stiffer, but it’s also far more accurate. I like this one a lot because it can handle more heat than others before it starts to be affected. It’s typically implemented for precision builds. Bulls are .936” in diameter.
- Medium (M4): The M4 contour possesses a cutout for grenade launchers which is what makes it ideal for military purposes. It’s got terrific balance and is .750” in diameter.
In my opinion, the average plinker doesn’t require anything more advanced than light or medium barrel.
Barrel Feed Ramp
This is a vital part of the AR-15’s upper receiver, therefore you want it to properly match the barrel of your rifle.
It is still debatable as to whether or not the barrel’s feed ramp affects reliability, but at the very least, it’s important to match the ramp with the upper receiver. Usually, if you buy factory-made rifles this won’t be an issue, but you should still check to confirm it.
Barrel Twist and Bullet Grain Ratio
When it comes to the AR-15, two critical factors can significantly impact its overall performance – the barrel twist and bullet grain ratio. Understanding their importance can help you make the right choice when buying an AR-15 or when selecting ammunition for your rifle.
Let’s start with the barrel twist. The term refers to the rate at which the rifling inside the barrel rotates the bullet as it’s fired. This spinning motion stabilizes the bullet in flight, improving its accuracy over long distances.
The barrel twist rate is expressed as a ratio, such as 1:7, 1:8, or 1:9. The first number refers to one complete rotation, and the second number is the length in inches that rotation takes. So, in a 1:7 twist ratio, the bullet makes one full rotation for every seven inches of barrel it travels down.
What type of barrel twist should I look for in an AR-15?
Choosing the right barrel twist for your AR-15 depends on the weight of the bullets you plan on firing, which brings us to bullet grain ratio.
The weight of a bullet is measured in grains, and this metric plays a crucial role in the AR-15’s overall performance. Heavier bullets, usually those over 62 grains, work better with faster barrel twist rates like 1:7 or 1:8. Lighter bullets, those under 55 grains, tend to fare better with slower rates like 1:9.
A bullet that’s too lightweight for a rapid twist rate might over-stabilize, and can even come apart mid-flight. Equally, too heavy a bullet with a slow twist rate may under-stabilize and lose accuracy over distance.
In essence, understanding how barrel twist and bullet grain ratios work is vital in optimizing the performance of your AR-15.
Here is a great barrel twist and bullet grain ratio to help you make sure you have the right combination.
No matter how the force is applied, it makes the bolt unlock, move back, eject the spent casing and pushes a new cartridge into the chamber.
By and large, most AR-15s are DI instead of Piston. Like most things, there are pros and cons to each.
Pros of Piston Gas System
- Typically more reliable in poor weather conditions (dust, water, moisture, heat, et al.)
- Relatively cleaner as dirty gas is vented out
Cons of Piston Gas System
- More expensive than DI
- Heavier with more weight in front
- Harder to find proprietary parts from manufacturers
- Less accurate than DI
Unless you’re in an Arnold Schwartzenegger movie where you have to fire your weapon coming out of water or you live in a desert somewhere, a DI system will be perfectly adequate for most purposes.
Assuming you properly maintain your AR-15, a DI model will be a dependable weapon.
DI Gas System Lengths
Gas system length is the distance to the gas hole. The gas hole refers to the triangular front site base (FSB) that sits on top of the barrel.
Although there is the rare “Dissipator” model that has a sixteen-inch barrel, the rifle-length gas system is normally used for an eighteen-inch barrel.
The average choice for sixteen-inch barrels is a carbine or midlength gas system.
Personally, I favor the midlength system because I think it’s advantageous because it enables the user to have a longer sight radius when you’re using a front sight base. You also get more rail space because the handguard extends from the upper receiver to that front sight base.
AR 15 Gas Blocks
We’ve mostly been talking about the FSB (Front Sight Base) style gas block here where the front sight is combined with the gas block and there’s a reason for that.
I always recommend this style to first-time shooters because it’s easier to have a front sight and it’s affordable to use a non-free-floating barrel.
Another good thing about this style is that it can be converted by grinding down the front sight base to allow for a free-floating barrel.
How the BCG (Bolt Carrier Group) Works
Alright, let’s cut to the chase and pull back the curtain on understanding how your firearm’s bolt carrier group (BCG) works. The bolt carrier group is like the heart of your AR-15, it’s responsible for maintaining the rhythm, the ebb, and flow of operations.
The bolt, the cam pin, and the firing pin, are the holy trinity of your BCG — everything revolves around these. The bolt’s where the magic happens — it houses the bullet, engaging and disengaging from your firearm’s barrel extension. Now, crack open that bolt, and you’ve got another mini puzzle of parts like extractor and the ejector.
Parts of the BCG
These small yet mighty parts may seem insignificant when you hold them in your hand, but they hold the power to transform your shooting experience. They are responsible for kicking out the spent casing after you fire and ensuring that your firearm reloads properly. Then, there’s your gas key and carrier, which plays a key role in the movement of the BCG within the firearm, essentially converting your gas operated system into a semi-automatic system.
The cam pin’s role is simple in theory, but crucial in execution. When you fire, the high-pressure gas propels it backward, causing the cam pin to rotate and unlock the bolt. Meanwhile, the firing pin is hitting the primer on the round, igniting the powder and sending the bullet out of the barrel.
It’s an orchestra of actions, each part flawlessly playing its role. It retracts when you pull the charging handle back. When you let go of the handle, the bolt carrier group moves forward, strips a round from the mag, and releases a round into the chamber. It’s no exaggeration to say the stakes are high as a slight glitch can quickly bring everything to a screeching halt. It’s awe-inspiring, seeing this industrial symphony in action — the sheer precision and scientific genius involved.
Semi-Auto vs Full-Auto BCG (Bolt Carrier Group)
Now, you might have hit a snag deciding on whether a semi-auto or a full-auto BCG is the right one for your AR-15. Let’s dive into what separates these two.
Size matters in the world of BCGs, and the full-auto version comes out as the heavyweight champion. It sports more metal at the rear end, which equates to increased weight overall. The reason for this additional heft is all about durability and reliability. Initially crafted for the fully automatic M16, the full-auto BCG can handle the higher rate of fire and heat generated by a fully-auto rifle, hence the additional metal.
Now, don’t get it twisted; the semi-auto variant is no slouch. It carries the same design as the full-auto, but it’s missing a chunk of metal on the underside of the carrier. The semi-auto BCG was built for lighter, more consistent use typical of civilian shooting.
Why would I consider the full-auto if I’m planning to shoot semi-auto?
So, you might be wondering, “Why would I consider the full-auto if I’m planning to shoot semi-auto? Isn’t that overkill?” I get you. Technically, the semi-auto BCG will run just fine in your AR-15. But, this isn’t just about need; it’s about longevity, reliability, and occasionally about legalities.
The extra weight on the full-auto BCG can help your AR-15 run more smoothly, due to the increased mass moving inside the gun during cycling. More mass equals less felt recoil, and that’s something any shooter can appreciate.
But, it doesn’t stop there. That extra chunk of metal on the full-auto BCG also tends to improve its lifespan. It offers more durability, and since the AR-15 design is quite ‘over-gassed,’ you can bet on your rifle cycling harder and faster than intended. Having a full-auto BCG can take the brute of this over-gassing with more grace, ultimately extending the life of your rifle.
Finally, as surprising as it may seem, full-auto BCGs are also more common on the market. Part of this is because of the military’s surplus, leading manufacturers to follow suit with their own production. As a result, it’s not only easier for you to source full-auto BCGs, but often also cheaper.
Is it illegal to have a full-auto BCG?
Now, before we wrap this up, let’s talk about the elephant in the room – legality. If you’re worried that simply owning a full-auto BCG would land you in hot water with the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), you can breathe easy. The legalities of BCGs depend on whether your firearm can shoot fully automatically, not whether it has the potential to.
BCG Coatings
Now, onto the coatings. Here we’ve nailed down four of the most common ones you’ll be coming across: Phosphate, Black Nitride, Nickel Boron, and Titanium Nitride.
Phosphate Bolt Carrier Group Coating
The good old phosphate coating. Rugged and tried-and-true, it’s been the standard for mil-spec rifles for ages. It does one hell of a job withstanding heat and reducing friction, keeping your BCG running smooth. However, it’s a bit of a dirt magnet, meaning cleaning your BCG is gonna be a downright chore. Plus, extra lubrication will be on your list.
Black Nitride Bolt Carrier Group Coating
Lately, Black Nitride’s been edging into phosphate’s territory. Tough as nails yet smoother than phosphate, it avoids much of the dirt-catching troubles of its predecessor, making your cleaning just that little bit more bearable. Durability is not its weak point either. You can expect that Black Nitride BCG to be dealing a deadly lead shower for years.
Nickel Boron Bolt Carrier Group Coating
Got a few extra bucks to spare? Then Nickel Boron might catch your eye. The step-up in slickness lets your BCG slide right into action, no extra lube needed. And that shiny silver finish makes identification of carbon build-ups easier than pie, meaning clean-up is a breeze. Heftier price tag? Sure. But for the reduced maintenance, it might just be money well spent.
Titanium Nitride Bolt Carrier Group Coating
Lastly, we’ve got the king of the hill: Titanium Nitride. It’s slick, it’s durable, and with its gold finish, it looks like something right out of a sci-fi flick. It’s got all the benefits of the Nickel Boron, but it’s harder and even smoother. Most importantly, it’ll last through whatever you can throw at it. Of course, it comes with a price to match its performance.
The Impact of Bolt Carrier Coating on AR-15 Performance
Each of these coatings brings its own to the table, impacting your AR-15’s performance in different ways.
Phosphate cuts down on heat and friction but demands good upkeep and a generous hand with the lube. Black Nitride, on the other hand, brings the same heat resistance to the table, with a bit less fuss on the cleaning and lubrication front.
Nickel Boron steps up the game with improved slickness and easier maintenance. The need for lubrication lessens, which means you’re running smoother for longer, especially when operating in arid or dusty conditions. The ease of cleaning also promotes longevity, which can result in a more reliable AR-15 over the long haul.
And Titanium Nitride? It’s the cream of the crop. The top-tier slickness means less grime, less friction, less heat, and thus, less wear and tear. Your AR-15 is gonna thank you for it, with every smoothly operating trigger pull.
When choosing the BCG coating, it all boils down to what you’re gonna get out of it. If you’re willing to put a bit of grit in for upkeep, Phosphate or Black Nitride might be your best pals. Else, if you’re a bit more free-handed with the greenbacks for lesser maintenance, you might
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