Bravo Company BCM4 Lower Receiver Assembly

I used to think that all lowers were alike, and that the only real difference in lower parts kits was that some came with fancy triggers.

I now know this to be false.

After having to perform final – perhaps corrective is a better term – machine work on several “budget” lowers, I started to set my sights higher. It’s easy to cut what would seem to be fat out of an AR-15 build budget by using a cheap lower and a cheap LPK. For many (low-volume) shooters, this is just fine. For those who want – or need – something better, and aren’t willing to depend on luck to guide them to a serviceable lower and a durable LPK, there are better options out there.

One of those options is the Bravo Company BCM4 lower. It’s only available in assembled form, and comes with excellent small parts. It sells for $360, but it’s worth every penny.

I’ll start at the back.

The stock body is made of the exact same materials, and has the same exact dimensions, as the buttstock on the Colt M4. The BCM stock even uses properly heat treated latch hardware. Want to change the factory stock anyway? Cool.

The receiver extension tube is made to the “mil-spec” diameter of 1.146″, enabling the owner to install the widest variety of aftermarket stocks, and ensuring the best thread engagement between the tube and the receiver. This isn’t the only feature – it’s also made from 7075-T6 aluminum, in exactly the manner prescribed by the government for military M4s, all the way down to anodizing and dry film lube on the inside. The one deviation is that it has six positions and thus offers a greater stock adjustment range.

The “castle nut” which keeps the stock in place is staked – in two locations – having had an unstaked castle nut come loose (which resulted in a nonfunctional weapon), this makes me feel warm inside.

The BCM lower comes with an H buffer – containing the proper tungsten weight inside – backed up by a quality action spring. The action spring is one of the most important – and most overlooked – parts of an AR-15.

Grease is applied to fire control group contact points, which helps wear the parts in.

The hammer isn’t notched, which aids in reliability with 9mm uppers and unshrouded firing pin carriers. The notched hammer will stop the weapon from firing more than one round with each pull of the trigger should the disconnector fail. In fact, it’ll stop the weapon from functioning at all after that happens.

“But,” you say, “I’m worried about having the weapon malfunction like that! Isn’t that an important safety feature?”

Well, if you’re concerned about the weapon malfunctioning in that manner, you should buy a lower that has its fire control parts made to the proper dimensions, made of quality materials, and properly case hardened. The BCM lower falls into this category. In my opinion, actively trying to prevent failure is better than trying to jerry-rig a suspect method of stopping the failure after it’s already happened.

A nice touch found on BCM lowers is the inclusion of an “enhanced” trigger guard that has been modified in order to allow a gloved finger to fit. When I shoot a lot, I wear nomex flight gloves that don’t take up a whole lot of room, but this is a nifty feature for those in the frozen north.

One final note: the BCM lower is now available with an A2 stock, and I would assume that it will be available with the Vltor A5 stock assembly shortly.

So, is the BCM4 lower right for you? Only you can make that decision. If the $360 price tag completely kills your budget, then you might have to look elsewhere. However, just as a strong foundation will ensure that a house stands for a long time, starting with quality, durable parts will ensure the long service life of a carbine. The BCM4 is about as “strong a foundation” as you can get. Now that you know what you’ll receive should you choose to plunk down 360 hard-earned dollars for one, you can make an educated decision about what’s best for your needs.