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First Gear | AR-15 Bolt Carrier Group

First Gear | AR-15 Bolt Carrier Group

As we wrap up a review of an exceptionally fine MSR/AR pattern 5.56/.223, we find ourselves wondering if our own rifle quite matches up. Of course, there’s nothing like a shiny, high-end example to make our checkbook itch, but the next thought is often along the lines of, “Is different the same as better?” To that, there may not be a definitive answer: Going head-to-head and across the board, there will always be pluses and minuses unless the starting points were wildly different.

Sharps Rifle Company offers their “Balanced” BGC complete with the patented Relia-Bolt lug system—S7 tool steel and NP3 make it a favorite. Photo by A1F Daily Staff.

That’s also what makes the Stoner/AR/MSR such a remarkable rifle: From hobbyist to competitor to duty expert, the design is nothing if not flexible. The downside of that versatility can leave you feeling like you’re trying to wet your whistle from a fire hydrant, however. Sighting, barrel/gas systems and furniture options are the most obvious variables, but some others live inside the rifle. These can have major effects on overall utility.

Net quality here has implications for improving both performance and longevity in Stoner-pattern systems.Enter your Bolt Carrier Group—or commonly, the BCG—the arguable heart of the MSR. Net quality here has implications for improving both performance and longevity in Stoner-pattern systems. Many MSR owners are a little intimidated by their BCGs: They rightly assess the importance, but wrongly the hinted-at delicacy or complexity. 

This isn’t fundamentally unwise, but should be tempered with real information. Like any manmade thing, they can fail. You occasionally hear “hobby” class rifle horror stories, and we don’t doubt their truth. But our own experience has been happily different. Our very first AR was the only one we ever had trouble with vis a vis the BCG (a staked, but still loose gas key that we failed to properly diagnose). Simply, the AR market is now so competitive that seriously bad rifles are sussed out in a hurry, and their sources rapidly disappear. But at a micro level, the BCG deserves the same attention as the rifle at buyin’ time: Do your homework, and choose for the workload your shooting requires. 

A typical BCG will be made of Carpenter 158 steel, and should be both shot peened (a process which “uniforms” the surface) and magnetic-particle inspected (which will reveal hidden flaws). Generally they will have a phosphate finish for corrosion protection, and will work just fine for the average bear. Service life will be in the 5,000- to 10,000-round range. Despite what you read/hear elsewhere, we’re of the “lube that sucker” school to assure that duration, no matter what your environment.… the BCG deserves the same attention as the rifle at buyin’ time: Do your homework, and choose for the workload your shooting requires.   

If you want better functional life—and we think, higher overall reliability from day one—seriously consider upgrading your BCG. Even modest rifles will perform better in every sense if you reduce friction, and this is the most obvious thing upgraded BCGs bring to the party—harder, slicker bearing surfaces. 

We’ve used a variety, including Nickel boron, NP3 (Robar), and TiN (titanium nitride), and prefer them in that order—though there’s far less difference between the last two than the first. Here, the life of the BCG goes up a factor of two, and becomes less external-lube dependent (as NP3 wears, for instance, “new” self-lubing polytetrafluoroethylene—Teflon—is exposed). Still lube? The argument rages, but keep in mind the opposing surface is not as hard and still needs corrosion protection, so we come down on the “yes” side. There are some newer coatings that report even higher lubricity, but we can’t comment on these out of our own knowledge just yet.

"SRC "balance" comes from less material at the rear, deeper relief up front. Runs like a standard BCG for us!. Photo by A1F Daily Staff.

 

There’s another incidental benefit to these advanced surface treatments. Their slickness means that the unavoidable by-product of smokeless power combustion—carbon—has a much more difficult time attaching itself to bolt and carrier. With phosphate finishes, a serious cleaning is a toothbrush and mumbled cursing affair. With high-lubricity coatings, it’s essentially “wipe and reassemble”—really! 

BCG mass is another tempting variable to play with, but we recommend serious consultation with an AR-savvy gunsmith before venturing too far ...BCG mass is another tempting variable to play with, but we recommend serious consultation with an AR-savvy gunsmith before venturing too far, moneywise. Lightweight bolts/carrier outfits (and appropriate springs, buffers and even ammunition) will make your rifle run faster, it’s true, but many a shooter won’t be able to tell the difference until their trigger skills are quite advanced. Like any “thoroughbred” configuration, the balance can grow precarious here. In our book, utter reliability trumps an impressive “gee whiz” coefficient every time. 

Two other benefits occur to us in the wake of a BCG upgrade. The first is somewhat philosophical, but with a practical manifestation: If you dump some extra cash into this component, perhaps you’ll want to understand and maintain it better—always a good thing. (Our friends at Brownells can help here.) 

The other bonus is purely practical—that old BCG. Shoot it 200 or 300 rounds, clean it, and then put it away. You now have a tested back-up, should your upgraded mainstay ever fail. 

The way things are looking, such an assembly may save a lot of trouble and “out-of-stock” or other anguish in the next few years.

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