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5 Best Lightweight Bolt Carrier Groups (BCG) [Hands-On]

Want to really reduce your double-tap split times? We've tried the most popular lightweight BCGs on the market and know which are the best after thousands of rounds.

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Looking to really reduce your AR double-tap times?

You'll want to go the lightweight low-mass bolt carrier group (BCG) route.

The BCG is the piece of metal moving back and forth between each shot.  Lower the weight...and you'll lower the disturbance to your rifle and sight picture.

We'll cover the most popular ones out right now, other upgrades you should do at the same time, and reliability concerns.

Sneek peak, here are our top picks for lightweight BCGs:

The Quick List

Table of Contents

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Why Get a Lightweight BCG?

As we mentioned above...lowering the mass of the primary thing moving around in your rifle is going to help minimize the overall movement.

This will let you get back on target faster and reduce the felt recoil.

AR-15 BCG Function
AR-15 BCG Function, 45Snipers

The normal advice is to use the full-auto (FA) BCG compared to the lighter semi-auto BCG when used in rifles where reliability is key.

And don't worry...full-auto BCG's are perfectly legal.  It's the trigger group that makes something actually full-auto.

The extra mass of FA BCG's keeps things running smoothly in over-gassed AR-15's that were made to run a variety of ammo and in crappy environments.

FA vs Semi BCG
FA vs Semi BCG (Left = Semi, Right = Full-Auto), TTAG

Since you're looking at lightweight BCG's...you're probably messing around with a secondary AR-15...likely for competition.

You probably won't be scrounging for ammo on the battlefield so you can lower the amount of mass needed to make your rifle still run 100%.

I know what you're thinking...

What about using the lighter semi-auto BCG?

It's only slightly less weight at 10 oz and change compared to the FA of 11.5 oz...while the ones we're going to talk about are getting down to the 5 oz range.

How Do You Lower the Mass of BCG's?

First...you can cut away "unnecessary" parts of the steel carrier.

And second...you can use more exotic materials that weigh less.

You'll see a mixture of these two types of mass lowering techniques in our roundup.

Speaking of which...let's get started!

Best Lightweight BCGs

We've tried out three of the most popular ones on the market...

Lightweight BCG's
Lightweight BCG's (Top to Bottom, Rubber City Armory, JP LMOS, Faxon)

1. JP Enterprises Low Mass (LMOS) BCG

JP Enterprises Low Mass (LMOS) BCG
Prices accurate at time of writing
$335at Brownells
Optics Planet (See Price)
  • Weight: 8.9 oz
  • Price: $335
  • Material: Steel
  • Notes: No serrations for use of the forward assist

JP was one of, if not the first, major company to sell lightweight BCGs.  For a while, they stopped, but now they are back at it again with their Low Mass Operating System (LMOS) models.

JP Ultralight BCGs
JP Ultralight BCGs

We're at around the 1000 round count and don't see any major wearing...just sweet low recoil shooting.  It's made of steel so it should keep on chugging.

Just keep in mind that you'll lose the use of your forward assist function (who has ever actually used their forward assist though?).

*EDIT* I originally stated that this model was aluminum.

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2. JP Enterprises Ultra Low Mass BCG

Lightest BCG
JP Enterprises Ultra Low Mass BCG
Prices accurate at time of writing
$356at Optics Planet
  • Weight: 5.8 oz
  • Price: $437
  • Material: Aluminum
  • Notes: Lightest BCG on the market today

This new BCG from JP recently came out so we haven't gotten our mitts on it yet...but we had to include it since it truly is ULTRA low mass.

But with great weight reduction comes great cost.

Both monetarily and reduced life.  Because the BCG is the same material as your upper receiver (aluminum)...it will see some wear and degradation as it does its job...to a point where you have to get a new one.  For that reason, JP recommends that you use the Ultra only in competition rifles.

It now has forward assist capabilities, but after a couple thousand rounds you'll have to junk it for a new one.

3. Faxon Lightweight BCG

Most Affordable
Faxon Lightweight BCG
Prices accurate at time of writing
$229at Rainier Arms
Faxon Firearms (See Price)
Brownells (See Price)
  • Weight: 8.5 oz
  • Price: $249
  • Material: Steel

From Faxon, maker of affordable and great barrels comes their lightweight steel BCG.  Check out all of those weight reducing cuts!

Since it's steel...the carrier should last almost indefinitely like its semi and full-auto brethren.

We've been running it in our overall super lightweight build for around 800 rounds and it's been running smooth as butter.

Lightweight Upper Build, Faxon and Brigand Arms
Lightweight Upper Build, Faxon and Brigand Arms

The price is right too at about $200 less than the normal JP aluminum BCG and even less weight.  Just good luck finding it in stock!

4. JP Enterprises LMOS Steel Carrier

Carrier Only
JP Enterprises LMOS Steel Carrier
Prices accurate at time of writing
$215at Brownells
Optics Planet (See Price)
  • Weight: 8.8 oz (with bolt)
  • Price: $215
  • Material: Steel
  • Notes: Carrier only...you'll need a bolt from somewhere else, plus no forward assist serrations

Since at the time of publication the Faxon was sold out everywhere...I'm throwing in JP's steel version for price-conscious lightweight aficionados.

The weight is on par and you'll save if you scrounge up a bolt from a previous BCG.

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5. Rubber City Armory (RCA) Titanium BCG

Editor's Choice
Rubber City Armory Titanium BCG
Prices accurate at time of writing
$304at Primary Arms
AR15 Discounts (See Price)

Thank you, titanium, for bringing the best of both worlds...the lightness of aluminum but the durability of steel.

Lightweight BCG's
RCA Titanium BCG (Top)
  • Weight: 7.8 oz (with bolt)
  • Price: $360
  • Material: Titanium

You'll shave off 32% of the weight compared to a standard BCG, but you won't run into the wear problems of aluminum carriers.

I've been running the RCA for over a year (estimate 2500 rounds) in my competition build and I'm still not tired of tapers showing me the touching double-taps I get on targets.

Readers’ Ratings

5.00/5 (4686 Votes)

Your Rating

6. Brownells Lightweight BCG

A newcomer from Brownells which usually has great self-branded stuff.  When you want to try out going lightweight without breaking the bank.

Comes in three flavors of Nitride, Nickel Boron (my recommendation), or TiN (gold...yea you know who you are).

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What Other Mods?

Since the AR-15 is a well-oiled machine where multiple parts have to work together...you can't just change up 30% of one thing without having to mod others.

Here's what I found to have the best reliability combined with a lighter BCG.

JP Captured Spring

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Gets rid of the *sproing* of the regular buffer tube spring...and makes your AR-15 feel and shoot SO much better.  Especially needed since the standard buffer and spring are too heavy/stiff for your lightweight BCG.

Opt for the spring kit if you decide to go this route.  I originally got the single pack and needed the lightest spring to go with my RCA BCG.

The kit lets you customize things to just how you like them.

Not ready to make the jump to the entire system...check out a lighter buffer ($57) and tuned spring ($19).

Superlative Adjustable Gas Block

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You'll really want an adjustable gas block since you'll need less gas to move the lighter BCG.  Otherwise, you'll have a really fast moving BCG which might actually increase felt recoil and damage parts.

My pick is for the Superlative Arms gas block (full review) since it has the bleed off hole technology.

Conclusion

Lightweight and Regular BCG's
Lightweight and Regular BCG's

So there you have it...our list of the best lightweight BCG's on the market right now.

Want more awesome AR-15 reviews and guides? Take a look at this!

If you have any questions about swapping your bolt carrier group out, how to choose a new one, or you just want to tell others how much better (or worse) you're shooting with a low-mass BCG, be sure to let us know in the comments below!

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Written By

Eric Hung

Eric Hung

Founder, CEO

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I'm Eric Hung, the founder of Pew Pew Tactical, and I love guns. For over 10 years I've been soaking up as much information as possible online, in competitions, classes, and from my own testing. Now I hope to bring that info to you! I've written over 250 articles on Pew Pew Tactical that are read by millions a month. I'm also an NRA certified pistol instructor and avid USPSA/3-Gun/NRL22 competitor. Learn more at About Us.

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Conversation

43 Comments

Join the discussion

  • I have the faxon lightweight gunner 16” barrel paired with the lightweight faxon bcg. Can anyone make any sense out of accuracy issues with multiple brands of ammo? Additionally, the accuracy is slightly better with 5.56 ammo.
    ...
  • 1
    Why can't someone make a right side charging lightweight bolt carrier group for the 223/5.56 SBR's that want to make a cycling semi-auto w/ subsonic ammo. The pistol length gas system should be able to direct enough gas to operate it with the appropriate buffer spring/weight. The carbine and rifle length systems don't seem to direct enough gas to use for this. I have tried to contact BCA about making one, but can't get an answer.
    ...
  • 2
    I think you left out a few points, it can be very tricky to get these guns to run using superlight BCG, such as aluminum. I am using a superlative GB, bleed off style with 40 something adjustments. Even with that I was overgassed (suppressed), ended up with a restrictive Gas tube to get it to run. One click on the GB and it us over/under gassed. Furthermore aluminum BCGs, wear quickly, typically where the hammer interfaces to cock. Aluminum BCGs are really meant for competition. Also aluminum BCGs are available for $160.00, or where last time I checked. Not from JP, but quality nonetheless.
    ...
  • 2
    Thoughts on the Battle Arms Development Titanium BCG?
    ...
  • 1
    1
    Hello will the same recommendations work for 308? And will anyone recommend do this for a 308? Thanks
    ...

    • Matt Greñas

      I'm putting a 2A Armament Ti BCG in my newest build, which will be my first "how light can I make it" rifle. Cool thing is it's adjustable through the gas port, no adj gas block needed (which being able to adjust gas is pretty much a necesity once you start meddling with internals to this degree). I can't in good conscious tell you to buy one yet, literally is going together this weekend; but the reviews are good, and I ahve a bunch of their parts and receivers on other builds and they're top-shelf for sure. Writing this because they also make an adjustable Ti .308 BCG as well. FWIW the adjustable AR15 Ti BCG is 5.93oz complete, 48% less than the full mass I typically run. Just looked, and their 308 Ti adjustable is 11.55, about 32% less than a typical full mass (and ironically the same exact weight as a full mass ar15 BCG lol).

      Just a little food for thought. People do it for sure. As others have said, it's not a dragon I'd chase on my first or second, "trust my life to it" rifle. But it's a fun experiment, and if you get running enough that it prooves itself to me/you, it could very well end up being that rifle (or, if nothing else, a great candidate to carry through the woods all day).
      ...

    • David, PPT Editor

      The AR-10 requires a much larger BCG, they are not compatible in any way :( Some of these companies also make AR-10 BCGs, but I haven't ever used or seen a lightweight AR-10 BCG. Due to the increased power you're working with, I would strongly recommend sticking with a normal BCG for .308 Win.
      ...

      • Courtney

        Actually there are a few Lightweight/Low Mass/Titanium BCG's out there for the AR-10 / 7.62, but good luck finding any of them now lol. Rubber City Armory Does make a Titanium and a low mass steel version according to their website, but both are out of stock at this time (shocker hahaha)
        ...
  • Thanks for the great input, I had not heard a bunch of information you presented in the building upper w low mass/wt BCG... I changed a barrel on an upper and no torque wrench, no shims/spacing devices, just kept tightening and it works, headspace was tight and was denting brass when I cycled before shot it. Got the go or no go? (Forgot which, have both now) so I would not blow myself up. Next one I will do right:)
    ...
  • 1
    Eric,

    Your comments here indicate these lightweight setups are for competition guns.

    Are they too unreliable or sensitive for a target rifle, hunting rifle or self defense rifle?

    Thanks,

    David
    ...

    • David, PPT Editor

      A lightweight BCG is great for a competition rifle that you're willing and able to give proper care and time in to, but I wouldn't put them in a hunting or self-defense rifle personally. Target rifle depends on what you're looking to get out of it.

      Due to the design, these BCGs can be a little finicky across different types of ammo and the gas system may require retuning between different loads. It is also just naturally less durable than a full-weight BCG.
      ...

      • David

        Thanks for the reply. It seems then the only option for a gun that may see some neglect would be a semi-auto bcg to save a little bit of weight.
        ...
  • Aluminum BCGs DO NOT necessarily have to have dramatically lower lifespans. Aluminum-on-aluminum is extremely high friction and wear. Yet, automobile engines have used aluminum pistons on aluminum cylinder blocks for half a century. Engines have cycles measured in thousands of RPMs, each of which represents two strokes of the pistons. This is with a crankshaft and rods slapping the pistons from side to side too, not a largely linear action like a BCG. The Secret?

    --

    IRON. The engines either have iron cylinder liners or they have an iron coating on the pistons themselves. TiN and all these "ultra hard" coatings are counter productive. The idea is to have the two surfaces have a low friction co-efficient. Sandpaper against sand paper wears even if sand is very hard. Lead-bronze against steel, not so much even though lead-bronze is NOT.
    ...

    • John

      Its not the aluminum on aluminum or aluminum in a composite upper, its where the BCG slides over the hammer to cock. This area will wear quickly.
      ...

    • NC_Libertarian

      Aluminum engine blocks have plated cylinder walls. There is no aluminum on aluminum friction surface in the cylinder/piston interface.

      Iron Coating on Pistons? I have no idea what you are talking about.

      Coatings on internal engine components are standard procedure for many wear surfaces in production engines, and for virtually every wear surface in a modern competition engine. So your generalized statement about coatings is categorically and provably false.

      Sandpaper vs. sandpaper, Bronze, vs. steel: I have no idea what point you are trying to make here. But there is a lot more to wear surface performance than hardness. Doubt me? Then why does an engine bearing have a babbitt surface so soft you can embed your figernail in it, yet can handle the loads generated by engines producing thousands of horsepower. In fact, hardness is one of the lesser factors. Surface characteristics, geometrical fitment, chemical interaction, temperature, lubrication, etc are what determine wear characteristics.
      ...
  • I have been running a Brownells lightweight BCG with an SLR adjustable gas block, and an Armaspec Stealth capture spring behind a midlength Faxon 14.5" pencil barrel, and with about 3000 rounds through it, I am pleased with this build's performance. Lightweight, yet little recoil or muzzle rise. These are definitely mods to be considered, for any type of build.
    ...
  • Eric

    Looking for a left handed BCG group, light weight, NIb -556 and 6.5 grendel II

    fallowed your page on light weight BCG's not alot out there in LH catagory. Young manufacturing has one that is chrome, but weight is at 10.

    Bolts, I can buy if need be, its just the carrier .

    Iron City Rifle works has a great looking line of RH BCGs but online page shows NO LH . need to call and ask if they can manufacture.

    same with Young.

    What our opion on ajustable gas keys vs ajustable blocks?

    Question " Do you know of any compainies that I may have missed? Or is this a NO NO to ask that question due to "promoting". Thanks
    ...
  • 1
    FYI, the Brownells low mass BCG WILL NOT run in a milspec tube. I ordered one for a custom pistol build and i could not pull back the charging handle. I tried in my rifle and it would cycle manually but with a lot of resistance and would be afraid to fire it. Brownells tech said it is intended for competition guns using commercial tubes. From ordering, to getting a refund after it was returned, it took almost 2 months! Not one person told me the same thing the entire wait. I even had to have my bank file a dispute.
    ...

    • Lee

      I have the Brownells Lightweight BCG and a milspec tube with a reduced power spring and it works just fine.
      ...