The Best AR-15 Bolt Carrier Groups: What They Really Cost

There are two schools of thought when choosing the best AR-15 bolt carrier group for your rifle. The first school says the bolt is the only thing between your face and a small explosion, so it should be high quality.

The second school of though takes a more…  relaxed view of things.

The second school says they’re pretty much all the same so get whatever is cheapest and it’ll work just fine.  And it’s true most of the time.

But sometimes…

Personally, I think the second school of thought is just plain stupid because for a few dollars more ($10-$20) you can get a VERY high quality BCG.

I only have one body and I plan on keeping it for a long time.

NOTE: This article is part of my "Best in Class" series where I list the top choices for various parts of your AR-15.  You can find the other parts here: Best in Class Articles.

Requirements for the Best AR-15 Bolt Carrier Group

(You can skip this section if you just want a recommendation and don’t care about the nitty-gritty tech stuff.)

I devoted a chunk of my AR-15 build guide article to the requirements for a great bolt carrier group. But I will repeat them here to save you a click and some scrolling.

The most important factors are the type of steel and the heat treatment.  Carpenter 158 steel and 9310 steel are the best choices and are fortunately the most common.  For a while, some people were making bolts out of 8620 steel which is NOT acceptable.  8620 steel is much weaker and you can break your bolt with hard use.

While you shouldn’t make the bolt from 8620 steel, It’s the correct steel for the carrier.  In fact, 8620 is mil-spec for the carrier and has worked perfectly for over 50 years.

It’s also very important to make sure the bolt carrier has a shrouded firing pin.

If you look at the picture, you’ll notice that you can see the firing pin on one carrier, but not on the other.  The left hand carriers have shrouded firing pins.

A shrouded firing pin is VERY important because without it, all the force used to cock the hammer is applied to the firing pin. 

An unshrouded firing pin causes excessive wear on both the firing pin and hammer and can easily break your firing pin with hard use.  By contrast, a shrouded firing pin allows the carrier to take the force and apply it more evenly to the hammer.

All “Full Auto” or “M16” bolt carriers will have a shrouded firing pins.  

To get the best bolt possible, there are three other things to look for.  (these only apply to the bolt, not the carrier) You want a bolt that’s HPI/MPI and shot peened.  “HTP” stands for High-pressure tested, MPI stands for “Magnetic Particle Inspected”.  Both are quality control measures that ensure you’re getting a high quality bolt.

Shot peening will ensure:

“the finished part will resist fatigue failures, corrosion fatigue and cracking, and galling and erosion from cavitation.”

For non-engineers, that means it will keep it’s strength over time. Now lets look at some great BCGs.

FYI: If you buy after clicking most of the product links on this page I'll make a few bucks.  It's not much, but it keeps the website going and I would appreciate your support. 🙂

Brownells M16 B-TAC BCG – $100

EDIT: The B-TAC BCG has been discontinued. However, Brownells does have a replacement BCG currently available for pre-order.  The only difference appears to be that it wasn’t tested with an over-pressure proof load. Omitting that step might account for the $10 lower price.  Obviously I haven’t tested one because it’s a pre-order.  However, given Brownells’ track record and lifetime guarantee I don’t *think* they’ll be any problems.  That’s just conjecture at this point though.

Every so often, you find a great product at an incredible price and that’s the case here.  The Brownells B-Tac BCG is hands down the best AR-15 bolt carrier group (for the money) I’ve ever seen.

(To be clear, I’m not saying this is the best BCG that anyone makes and it beats all others in quality.  But it has everything done right for a price that’s almost unbeatable.)

To quote from them:

• Every Bolt is High Pressure Tested (HPT) with a proof load
• Following the High Pressure Test, every Bolt is Magnetic Particle Inspected (MPI)
• The Bolt is machined from 9310 steel
• Following machining, the Bolt is heat treated and shot peened
• M16 Bolt Carrier is machined from 8620 steel and hardened
• M16 Bolt Carrier will function in semi-auto or full-auto AR-15/M16
• Gas Key Screws are properly torqued and staked

It checks every single box and is only $100. 🙂

Even better is the finish.

The mil-spec finish for the bolt and bolt carrier is called “parkerizing“.

Parkerizing is fairly corrosion resistant but is also extremely porous.  The surface is not smooth, but is full of tiny (microscopic) holes like the surface of a sponge.  These pores soak up and hold oil very well, which accounts for most of the corrosion resistance.

However…

The porous surface is also relatively rough.  That leads to increased friction and heat during operation.  Also, those pores love to get clogged with dirt and carbon.  Because of that, it’s harder to clean a parkerized surface than many other surface treatments.

Instead of the mil-spec parkerizing, they gave this BCG a nitride finish. 

Both Melonite and Tenifer are names for nitride treatment and both are widely used in industrial applications and on gun parts, especially pistol slides.  (Glock uses the Tenifer and S&W uses Melonite on the M&P series.)  If you want some more information, I found a Youtube video to give you a better idea.

The short version: it’s one of the two best BCG finishes available.

Nitride treated steel is very smooth, very hard, and extremely resistant to corrosion.  The smoothness is a great thing because it reduces friction, which reduces heat too.  Also, nothing sticks to it very well meaning it’s much easier to clean.  Plus, it’s a treatment not a plating/coating so it can’t chip, crack or peel.

All things considered, this is probably the best AR-15 bolt carrier group for the money.

And if it doesn’t float your boat for some reason, just take advantage of the Brownells “100% forever” guarantee.

If you aren’t completely, 100% satisfied with any purchase you receive from Brownells, for any reason, at any time, return it for a full refund or exchange. No hassle, no problem. And, we won’t bog you down in endless paperwork. Your complete satisfaction with each and every product we sell is what’s most important to us.

With a warranty like that, how could you go wrong?

BCM (Bravo Company Manufacturing) M16 BCG – $169

If you want a combat proven BCG, look no further than the BCM M16 Bolt Carrier Group.  BCM has acquired a well-deserved reputation for making very high quality parts.

In fact, BCM’s about page says:

Bravo Company USA, Inc.’s Previous Customers Include:

HQ SOCOM (Special Operations Command), US Army, US Navy, US Air Force, US Marines, US Coast Guard, various Special Operations Units, Department of Homeland Security, US Border Patrol, American Embassies, Private Security Companies, Law Enforcement Agencies and Tactical Units, and responsible civilians.

Needless to say, they get the details right.

You can look at any review anywhere, and you’ll find plenty of people who are so happy they won’t buy anything else.  That – plus the fact that our military and even special forces have used their products – should tell you something.

In fact, BCM takes quality control so seriously that they fire ever BCG before they ship it out.  (So it might have marks and/or be dirty when you get it.)  Objectively speaking, I can’t point to anything that says the BCM is any better than the Brownells other than the name.

But the name counts.

BCM has a great reputation for a reason.

Many people have tried it, (torture) tested it, and it’s absolutely top shelf.  It just plain works no matter what.  So if you kick down doors for a living, I’d take a hard look at them.  If not, I’d save almost $70 bucks and get the Brownells BCG

At this point, I run into a problem

In my Best in Class series, I usually list about a half dozen products at different price/quality levels to give you options.

However…

You won’t gain much from a more expensive bolt carrier group.  The only way up from here (and not everyone agrees it’s going up) is a Nickel Boron plated BCG. (and possibly Nickel Teflon, but the jury’s still out on that.)  However, Nickel Boron is hard to coat properly and only a few companies do it right.  Those companies charge at least $150, and usually more like $180 – $200.

Side note: if you see a Nickel Boron BCG for under $150 – and especially under $100 – I would stay away.  The odds of them doing the plating correctly are very low.  Cheap Nickel Boron plating can crack, chip or peel and cause function issues.

Both Nitride and Nickel Boron are much easier to clean than the standard parkerized finish.  I’d give the edge to Nickel Boron, and I’ve never needed anything more than a paper toil and a little CLP to get one clean.  Nitride isn’t exactly hard to clean either.  Both are light years ahead of the traditional parkerized finish.

Overall, Nickel Boron plating (when properly applied) is arguably better than Nitride, but it’s not twice as good.  (Not even close.)  So is it worth almost doubling the cost?

In most cases I would say no.

There are other coatings on the market, but most of them just don’t have the longevity of Nitride and Nickel Boron.

• Chrome plating.  Good, but chrome is a lot stickier than most people think.  My grandfather was a Hydraulic engineer at Caterpillar for decades, so he knows a thing or two about it. (they chrome plate the pistons).  Long story short, Nitride is a better way to go.  It causes less friction, can’t crack, chip or peel, and is usually cheaper too. (NOTE: the inside of the BCG’s gas key is almost always chrome plated per mil-spec)
• TiN (Titanium Nitride).  Not a good choice.  The most common use you’re probably familiar with is coating drills bits.  While the gold color is pretty cool, the coating is very thin and prone to wearing off quickly.
• IonBond and other PVD (Particle Vapor Deposition) Coatings.  They apply carbon to a surface in a manner that makes its’ structure resemble a diamond.  Diamond is one of hardest, strongest and slickest materials we know of, so the theory sounds good.  I bought a PVD coated BCG to test.  However, I got a warranty replacement after less than 200 rounds because the finish was coming off.  I haven’t tested the new one yet.  I would avoid PVD coatings at this point.
• Nickel Teflon (NP3).  I still haven’t made up my mind about this one.  Nickel Teflon is more slick than most platings, but it’s also much softer.  I have a Nickel Teflon coated buffer on my AR-15 and it has a few small dings from the buffer retaining pin.  I’ve heard it wears well on a BCG, but I don’t have enough evidence to say Yea or Nay right now.  They will run you almost $200.

That covers advanced BCG platings/coatings, and below is one I do actually recommend.

WMD Guns M16 NiB-X Bolt Carrier Group – $189

If you want to get a Nickel Boron Bolt Carrier Group, the only company I’m sure plates them correctly is WMD Guns. That said, if you buy from any of the tier one makers, you should get something good.

WMD Guns has their own proprietary version they call “NiB-X”. Their NiB-X plated M16 BCG is the one I recommend if you want a Nickel Boron BCG.

One more thing:

No matter what the advertising says, please don’t EVER run your AR-15 dry (no oil) no matter what coating/plating you have.

There is a VERY large gap between what “can” be done, and what “should” be done.

Can you run Nickel Boron BCG without oil and be reliable?  Yes.  However, you should never run any BCG without oil.  Even if the BCG doesn’t suffer, the upper receiver should definitely have oil regardless of the BCG.

Conclusion

For the vast majority of us, the Brownells BCG for $100 is probably the best choice.  It’ll work well as the heart of your AR-15 without draining your wallet.  If you ever have a problem, Brownells has their 100% forever guarantee to take care of you.

If you’re an LEO or military, the BCM gives you a lot of confidence in your equipment.

And that’s about all I have to say.

The best AR-15 bolt carrier group for you might not be the best for me. So pick the one that fits your needs and happy shooting. 🙂