PBA Enhanced AR-15 BCGs: A Story of Obsession

The bolt carrier group is the heart of the AR weapon system. Arguably, it is the most important moving part of the gun.  Because of this, we spent a little extra time and effort searching for the right BCGs for our guns.

Our Enhanced AR-15 BCGs are purpose built from the ground up to ensure absolute reliability and top-level performance. The story of how we got there is one of stubborn determination and uncompromising expectations.  And it almost didn’t happen (several times).  In the end, we are very please with how things turned out.

Our Requirements

We went into this process with what we thought were reasonable requirements (most of which are simply Mil-Spec, as denoted by an asterisk).

  1. Mil-Spec or better on all materials (metallurgically speaking).
    • 8620* carrier
    • Carpenter 158* bolt head
    • 4140 gas key (Mil-Spec: 4130*)
    • 4240* or 4340 extractor
    • S-series tool steel* ejector
    • 4340* cam pin
    • 8640* or 8740 firing pin
  2. Mil-Spec treatment and testing of all components, as applicable.
    • Heat treatment* per Mil-Spec, as applicable
    • Shot-peening* per Mil-Spec, as applicable
    • Proof high pressure testing of every bolt head*, per Mil-Spec
    • Magnetic particle inspection of every bolt head*, per Mil-Spec
  3. Mil-Spec or better finish of all components.
    • Chrome-lined carrier* and gas key*
    • Phosphate extractor*, extractor pin*, ejector*
    • Phosphate* or better carrier, bolt head, cam pin
    • Chrome firing pin*
  4. Gas key sealed with Permatex Aviation Gasket*, per Mil-Spec.
  5. Michiguns Optimized Carrier Key Screws (O.C.K.S.)
    • Properly staked (twice per screw)
  6. Sprinco springs and rings.
    • 5-coil extra power extractor spring
    • Ejector spring
    • Gas rings
    • Viton CRANE O-ring

We Looked; We Didn't Find

A Word of Caution: Mil-Spec vs. "Mil-Spec"

On the hunt for an off the shelf solution, we found something quite aggravating.  If you read nothing else on this page, read this: the consumer should be skeptical of the use of the term “Mil-Spec” by consumer-grade manufacturers. Many companies claim to offer “Mil-Spec”. When you confront them over the fact that materials, treatments, testing, finishes, etc. are less than Mil-Spec, you are met with “well, our products are Mil-Spec adjacent.”

Image: flickr

The Military has defined the Mil-Spec standard for the AR based on several decades of experience with the weapon system, with the ultimate goal of reliability and functionality for our soldiers.  Don’t question the legitimacy of the Mil-Spec standard as a foundation for everything in a combat weapon system. Mil-Spec should be the minimum standard for everything in the AR and anything that deviates from it should be approached with a healthy dose of skepticism.

Mil-Spec is apparently a high bar in the consumer BCG market, because very few commercial manufacturers bother to achieve it.  So, unless you are ordering BCGs from a company who supplies the U.S. military, don’t buy Mil-Spec claims at face value.

We pretty much knew what we wanted going into this process.  We searched high and low. And we didn’t find anything in the consumer market that met our expectations.  Where there were acceptable (though still less-than-perfect) options from a material/finish/treatment/testing/quality perspective, we ran into a couple of issues:

  • Issue 1: Prices were excessive.  We will not try sell you a no-frills $214 simply Mil-Spec phosphate BCG that should be half that price and cost the seller $50 to have built for them.  We will not try to sell you a $600 BCG when a $150 BCG is just as good or better.
  • Issue 2: The manufacturer couldn’t guarantee specific materials for the components (if they even knew what the materials were).
  • Issue 3: The manufacturer couldn’t meet consumer demand.  While there are some really cool options out there, featuring fancy carriers and bolts made of unobtanium that the manufacturer can’t even deliver doesn’t help the consumer, our business, or our mission.

So, we had to think differently.

Wading into OEM

Because the consumer market was a bust, we shifted focus to OEM custom assemblies.  We reached out to 6 OEM manufacturers.  In alphabetical order, these included AO Precision, Azimuth Technology, Microbest, Outerwild/DRG, SCT, and Toolcraft.  We had some simple criteria for filtering the prospects (before we even got into the nitty gritty of capabilities and detailed specifications):

  1. They had to actually respond to our request for proposal.  The only one that did not respond was Outerwild/DRG (this is the only one we will call out by name).
  2. They had to have production capacity for us.  One prospect was so small that they couldn’t even handle an initial 100 piece order.
  3. They had to offer Carpenter 158 bolts.  9310 and S7 are not suitable alternatives to the Mil-Spec C158 (we are happy to debate this with data and facts).
  4. They had to offer high pressure proof testing and magnetic particle inspection of 100% of the bolts.
  5. They had to offer the carrier, bolt head, and cam pin in our selected finishes (phosphate, chrome, DLC).

The table below summarizes the initial assessment (note that the masked companies are not in any particular order).

In the end, only one manufacturer made the initial cut.  And it happens to be the manufacturer we gravitated to from the start.

If you’ve never heard of Microbest, that’s OK.  Go spend 10 minutes searching “best BCG” on discussion boards and forums and you’ll get a feel for their reputation.  Microbest’s individual BCG sub-components, quality, and testing standards meet or exceed Mil-Spec in every way.  Everyone who knows the name, knows what it stands for.

Microbest offers a phenomenal selection of OEM options in various finishes.  And every option meets or exceeds Mil-Spec.

Microbest understands the benefits of a lean and agile production.  They are able to accommodate individual clients’ needs pretty well (and without 250,000 piece minimum order quantities).

Microbest has some of the best quality control in the business.  We still inspect and gauge the crap out of incoming components, but we reject very little that comes to us from Microbest, and we’ve never found an out of spec dimension.

The Perfect Solution: The Best of Everything

We knew exactly what we wanted: the best of everything.  Unfortunately, it wasn’t available in any one place (this would have been a much shorter story if it was).  In the end, we found and got everything we wanted, but we had to establish a relationship with 3 separate companies to do it.

First, we established a relationship with Michiguns for their second-to-none Optimized Carrier Key Screws (O.C.K.S.).  From the beginning, this enhancement over the Mil-Spec grade 8 screws was a non-negotiable requirement for all PBA BCGs.  We are not aware of any OEM manufacturer who currently offers O.C.K.S. as a standard option.

We’ve already thoroughly introduced the second company.  In Microbest, we found the rock solid foundation we were looking for (the same rock solid foundation that our $214 Mil-Spec competitor found).    With the exception of springs, rings, and screws, we use all Microbest components in our builds.  Microbest uses the Mil-Spec as their basis for materials, which makes everything else easy.  Microbest performs the proof high-pressure testing and magnetic particle inspection of our bolt heads, and assembles the gas key onto the carrier (using our O.C.K.S.).

The last company that we insisted on working with is also no stranger to quality and is the absolute leader when it comes to springs.  We wouldn’t give an inch on our requirement for all Sprinco springs and rings throughout, which created a challenge.  But any company that puts the effort that Sprinco/Tactical Springs does into a tiny, hidden component has our attention and affection.  We use Sprinco for all of the things that you rarely see, but will quickly put you out of commission if they fail.  You will find Sprinco 5-coil extractor springs, ejector springs, gas rings, and extractor O-rings in all PBA BCGs, because we refused to compromise performance and reliability just because it is tiny and hidden.

We believe that the marriage of the quality and precision of Microbest with the quality and longevity of Sprinco and the bombproof security of Michiguns O.C.K.S. results in some of the finest and most reliable BCG assemblies available.  And dollar-for-dollar, our BCGs deliver phenomenal value to the consumer.  In the end, the fight was worth it.

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