Bolt carrier for precision AR-15

Lone star Shooter

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Looking for recommendations on the type of bolt carrier for a precision AR-15 in 6mm ARC. Having a 20” Bartlein barrel with rifle +1” gas system spun up. Going to run a Superlative Arms adjustable gas block.

I am running FA BCGs on all of my other AR-15s
 

ormandj

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I have a pair of AR15s in 6mm ARC, with a 10.5" and 18" Bartlein, both with Superlative AGBs. Both have Toolcraft (OEM for most of the BCGs you see out there) DLC BCGs and bolts, which I've been happy with. That said, any of the major BCG manufacturers with quality products will be fine.
 

drewthebrave

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If you can get a headspaced bolt from your barrel maker, go with that option. If not, I've had good luck with SixFiveArms bolt in my Grendel (same bolt for the 6ARC).
 
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Lone star Shooter

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I ordered a properly headspace bolt with the barrel. My question is what carrier is best for a precision rifle. Everything else I have has the M16 full auto style carrier. Do the reduced mass carriers provide any benefit, especially with an adjustable gas block where the gas system can be correctly tuned?
 

ormandj

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I ordered a properly headspace bolt with the barrel. My question is what carrier is best for a precision rifle. Everything else I have has the M16 full auto style carrier. Do the reduced mass carriers provide any benefit, especially with an adjustable gas block where the gas system can be correctly tuned?

I still stand by my suggestion. :) I wouldn't go reduced mass unless you like reduced reliability in different operating conditions. I like a nice H2/H3 weight buffer, normal spring, normal BCG, and adjustable gas for my rifles (which I shoot suppressed). The lighter weight stuff is neat for game guns, but you can have nearly the same recoil impulse with the adjustable gas system, but without giving up the reliability since you have a full mass carrier and spring/buffer to put rounds into battery.

My nice AR15 rifles are sub-half-moa shooters, beyond that I move to bolt rifles.
 
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Ape_Factory

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Take a look at Rubber City Armory BCG's. Their proprietary coating is absolutely amazing (no lube, super easy to clean) and they have the option of adding a POF roller cam pin for reduced wear on the upper. They have both lightweight and normal weight BCG's, two different lightweight carriers, "normal" light and then ultra-light. They also offer carriers with adjustable gas keys in lieu of a gas block on the barrel. I find 2A's adjustable carrier better because the adjustment can be made without removing the carrier from the upper.

I'm using RCA's titanium lightweight carrier and haven't had an issue cycling anything. I've been testing various bullet weights and and loads, everything from 50gr VMAX all the way to 77gr SMK's and everything in between. It's never failed to cycle and lock the bolt back after I dialed in the gas via an adjustable gas block. I haven't touched the gas adjustment since the initial setup with the only caveat being I haven't shot in cold temps since I'm in Texas. I typically shoot in temps ranging from say 50 degrees to 100 degrees Fahrenheit.

 
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drewthebrave

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I ordered a properly headspace bolt with the barrel. My question is what carrier is best for a precision rifle. Everything else I have has the M16 full auto style carrier. Do the reduced mass carriers provide any benefit, especially with an adjustable gas block where the gas system can be correctly tuned?

Changing the weight of the carrier will not affect precision. It could affect the reliability, and it will affect the "feel" of the recoil impulse. As far as "best" goes, that's entirely subjective. I've noticed no difference in precision in the carriers I've used from PSA, Wilson Combat, JP, Aim Surplus, and Anderson Mfg. You can spend more on Rubber City, JP, etc., if you want better quality control, fit & finish, unique coatings, or extra features -- but you shouldn't expect any measurable variation in precision based on the carrier itself (assuming it's not total junk).
 

JS8588

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There is some evidence that supported carrier designs such as Lantac, San Tan, Sharps Rifle Company, CMC etc may lock up tighter with less play in the upper thereby yielding a marginal increase in precision. Of the ones I've tried, lantac definitely has the tightest lock up. That would be my choice. @MSTN seems to be using San Tan a lot these days after previously being a fan of Young Mfg & JP BCGs. Perhaps he can opine.
 

LRRPF52

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There is some evidence that supported carrier designs such as Lantac, San Tan, Sharps Rifle Company, CMC etc may lock up tighter with less play in the upper thereby yielding a marginal increase in precision. Of the ones I've tried, lantac definitely has the tightest lock up. That would be my choice. @MSTN seems to be using San Tan a lot these days after previously being a fan of Young Mfg & JP BCGs. Perhaps he can opine.
One of the issues we saw with the earlier Young’s chrome carriers with the enlarged OD to the carrier rails was sluggish cyclic rate and failure to feed + short stroke malfunctions due to the increased coefficient of friction.

That’s the thing you have to watch out for with “precision carriers” in the AR. Some carrier designs increase the surface area of the carrier rails, which will also increase the coefficient of friction. To get the coefficient of friction back down to the standard carrier value, they make the surface smoother with a highly polished nitride or some other coating.

I usually polish my carrier rails anyway to establish a “worn-in” smoothness from the start.

Mil-Std/TDP upper receivers have a dry film lube baked onto the inside of the carrier raceway to help suspend thick lubricant for longevity of optimum cyclic rate and reliable function, which is one of the most overlooked aspects of making upper receivers in the after-market. They are also held to a very tight tolerance on ID (Inner Diameter) and receiver face squareness.

I participated in a long-term study conducted by a foreign army on AR-15 carrier coatings run in Arctic conditions over 3 years, with high-volume shooting training throughout each year. Temps ranged from 72˚F in the summer down to -22˚F (-30˚C) in the long winter.

We tested standard Mil-Spec BCM, Titanium Nitride, hard chrome-plated, and Nickel Boron carriers. Keep in mind BCM carriers are held to TDP gauge-tested tolerances in the 3 critical bore diameters within the bolt bore, so they are extremely reliable and not representative of the vast majority of carriers in the civilian market. Notice the 3 different IDs here with the initial bolt alignment bore, gas ring compression bore, and bolt tail bore:

iu


Short story was there really wasn’t any performance advantage in reliability with the specialty coatings compared with standard Mil-Spec carriers. All carriers were lubed, so there wasn’t any corrosion observed on the phosphate mil carriers. Some participants felt that it was easier to wipe down chrome, TiN, and NiB carriers, but residual burnished discolorations were the norm on the bolt tail that forms the gas expansion portion of the Stoner Internal Expansion System. That addresses reliability.

For accuracy, the enlarged carrier rail OD should mechanically provide superior lock-up with the bolt, and I believe Les Baer did something similar with his AR-15s, in addition to many other accurizing techniques.

Any time you tighten up the articulating parts, reliability is usually sacrificed so some method to mitigate the tightness needs to be considered. KAC used a FAL-type sand-cut interrupted carrier rail design on some of their carriers for a while. Not sure if they are still doing it. My whole take on carriers is that I want reliability first and foremost.

iu
 

JS8588

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One of the issues we saw with the earlier Young’s chrome carriers with the enlarged OD to the carrier rails was sluggish cyclic rate and failure to feed + short stroke malfunctions due to the increased coefficient of friction.

That’s the thing you have to watch out for with “precision carriers” in the AR. Some carrier designs increase the surface area of the carrier rails, which will also increase the coefficient of friction. To get the coefficient of friction back down to the standard carrier value, they make the surface smoother with a highly polished nitride or some other coating.

I usually polish my carrier rails anyway to establish a “worn-in” smoothness from the start.

Mil-Std/TDP upper receivers have a dry film lube baked onto the inside of the carrier raceway to help suspend thick lubricant for longevity of optimum cyclic rate and reliable function, which is one of the most overlooked aspects of making upper receivers in the after-market. They are also held to a very tight tolerance on ID (Inner Diameter) and receiver face squareness.

I participated in a long-term study conducted by a foreign army on AR-15 carrier coatings run in Arctic conditions over 3 years, with high-volume shooting training throughout each year. Temps ranged from 72˚F in the summer down to -22˚F (-30˚C) in the long winter.

We tested standard Mil-Spec BCM, Titanium Nitride, hard chrome-plated, and Nickel Boron carriers. Keep in mind BCM carriers are held to TDP gauge-tested tolerances in the 3 critical bore diameters within the bolt bore, so they are extremely reliable and not representative of the vast majority of carriers in the civilian market. Notice the 3 different IDs here with the initial bolt alignment bore, gas ring compression bore, and bolt tail bore:

iu


Short story was there really wasn’t any performance advantage in reliability with the specialty coatings compared with standard Mil-Spec carriers. All carriers were lubed, so there wasn’t any corrosion observed on the phosphate mil carriers. Some participants felt that it was easier to wipe down chrome, TiN, and NiB carriers, but residual burnished discolorations were the norm on the bolt tail that forms the gas expansion portion of the Stoner Internal Expansion System. That addresses reliability.

For accuracy, the enlarged carrier rail OD should mechanically provide superior lock-up with the bolt, and I believe Les Baer did something similar with his AR-15s, in addition to many other accurizing techniques.

Any time you tighten up the articulating parts, reliability is usually sacrificed so some method to mitigate the tightness needs to be considered. KAC used a FAL-type sand-cut interrupted carrier rail design on some of their carriers for a while. Not sure if they are still doing it. My whole take on carriers is that I want reliability first and foremost.

iu

Had OP asked about "most reliable", I'd have answered differently. He didn't. He asked about precision.

The carrier doesn't really impact precision all that much, but it may effect it some.

OP has a barrel easily capable of sub MOA accuracy. I doubt he's going to be running tactical drills with a 20 inch Bartlein, which is why I omitted my usual "adjustable gas blocks invite reliability issues" comment.
 

LRRPF52

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Had OP asked about "most reliable", I'd have answered differently. He didn't. He asked about precision.

The carrier doesn't really impact precision all that much, but it may effect it some.

OP has a barrel easily capable of sub MOA accuracy. I doubt he's going to be running tactical drills with a 20 inch Bartlein, which is why I omitted my usual "adjustable gas blocks invite reliability issues" comment.
No, I appreciate your comments. Looking at the LANTAC, they definitely reduced coefficient of friction with their coating, and you can see the enlarged rail contact surfaces, in addition to something going on with the carrier tail:

iu


They also have the re-profiled and coated cam pin, which seems designed to eliminate the cam pin binding within the cam pin recess in the upper. Looks like they’re using US grade 8 fasteners with good stakes as well.

Has yours run reliably?
 
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JS8588

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No, I appreciate your comments. Looking at the LANTAC, they definitely reduced coefficient of friction with their coating, and you can see the enlarged rail contact surfaces, in addition to something going on with the carrier tail:

iu


They also have the re-profiled and coated cam pin, which seems designed to eliminate the cam pin binding within the cam pin recess in the upper. Looks like they’re using US grade 8 fasteners with good stakes as well.

Has yours run reliably?

Only about 250 rounds on mine so far (bought it this year & ammo availability has been...well, you know)

No issues, but I'm not shooting in the arctic!

Your experience & insight are impressive. I'm just a hobbyist.

I'm glad you didn't take my comment as being critical. You've likely forgotten more about the AR Platform than I've ever learned.
 

LRRPF52

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Only about 250 rounds on mine so far (bought it this year & ammo availability has been...well, you know)

No issues, but I'm not shooting in the arctic!

Your experience & insight are impressive. I'm just a hobbyist.

I'm glad you didn't take my comment as being critical. You've likely forgotten more about the AR Platform than I've ever learned.
Not at all. I’m always trying to learn more about it. I just started studying everything available while shooting the AR-15 since the 1980s. I’m happy to pass-on what I’ve experienced and learned so we all are elevated, just as those before did for me.

There are a lot of things right under our noses just waiting to be discovered with a little more digging. When I do a build now, it doesn’t even feel like the same gun. I see all the parts groups performing the same functions, but the way I assemble and screen through parts is so different, it might as well be something else.

Looks like LANTAC made a limited edition 6.5 Grendel as well.

Based on LANTAC’s specs on their Enhanced Carrier, they are using the flared bolt tail to help with alignment of the entire carrier.

They’re also using more forward-directed gas relief vents on the carrier.
 
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Dino11

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Take a look at Rubber City Armory BCG's. Their proprietary coating is absolutely amazing (no lube, super easy to clean) and they have the option of adding a POF roller cam pin for reduced wear on the upper. They have both lightweight and normal weight BCG's, two different lightweight carriers, "normal" light and then ultra-light. They also offer carriers with adjustable gas keys in lieu of a gas block on the barrel. I find 2A's adjustable carrier better because the adjustment can be made without removing the carrier from the upper.

I'm using RCA's titanium lightweight carrier and haven't had an issue cycling anything. I've been testing various bullet weights and and loads, everything from 50gr VMAX all the way to 77gr SMK's and everything in between. It's never failed to cycle and lock the bolt back after I dialed in the gas via an adjustable gas block. I haven't touched the gas adjustment since the initial setup with the only caveat being I haven't shot in cold temps since I'm in Texas. I typically shoot in temps ranging from say 50 degrees to 100 degrees Fahrenheit.


I second the Rubber City BCG, after running one I will never use anything else. They are local to me and give me dealer pricing on the stuff I walk in and buy. The owner is a super nice and smart guy. They have a proprietary Nitrided finish that has to be the slickest finish I have seen, you could probably run it dry without lube. Definitely top notch stuff. I have over 700 rounds through one and it shows very little to no signs of wear, not even the cam pin. Really tough Nitrided surface. They call it Enhanced+ Nitride.
 
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YammyMonkey

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Not a fan of the Lantac BCGs on the whole. While the forward venting gas ports are a little helpful as a left hand shooter who rarely shoots anything without a can, the coating causes lube to fling off and they gauge tight on headspace, refusing to close on a go gauge in several known quality barrels.

Between the coating & tight headspace, they required much more frequent lubrication than a standard BCM BCG.
 

Ape_Factory

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I second the Rubber City BCG, after running one I will never use anything else. They are local to me and give me dealer pricing on the stuff I walk in and buy. The owner is a super nice and smart guy. They have a proprietary Nitrided finish that has to be the slickest finish I have seen, you could probably run it dry without lube. Definitely top notch stuff. I have over 700 rounds through one and it shows very little to no signs of wear, not even the cam pin. Really tough Nitrided surface. They call it Enhanced+ Nitride.

I actually have been running mine dry as of late with no signs of wear. But I'm also not doing mag dumps or what I'd call heavy use given the current ammunition situation.

LRRPF52, any experience with DLC or what RCA calls their enhanced nitride +? DLC is a big step up from titanium nitride and I have lots of experience with it in the automotive world but their nitriding process seems to be even beyond DLC plus they have a bonded PTFE process. I wonder how long the PTFE lasts as it doesn't have a very high melting point although I don't think the BCG would ever reach 600F in semi-auto mode.
 

loveha

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    The two rifles I built have one of the Mystic Black BCGs, and I have a spare BCG with spare parts.
    Not much of anything sticks, oil, grease, carbon, doesn't matter. Wipes right off, if money wasn't going to building my reloading set up, I would get a Mystic Bronze just to replace my factory DD BCG.

    I think as far as specialty coatings go, they are probably the OEM. At least that is the feeling I get when I read the about page. Probably wrong about that though.
     

    BoDuke80

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    I would say get a top end MFG carrier the options and optinions are endless. Most important is get a bolt matched to your chamber by the barrel maker. Last 2 barrels I purchased with matching bolts and will nvr get one without again. What really changed my opinion was my 6.5 Grendel. Had a really good bcg but the bolt was a touch loose causing wild flyers. Replaced the bolt and it's a laser.
     

    ctrock

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    I have a pair of AR15s in 6mm ARC, with a 10.5" and 18" Bartlein, both with Superlative AGBs. Both have Toolcraft (OEM for most of the BCGs you see out there) DLC BCGs and bolts, which I've been happy with. That said, any of the major BCG manufacturers with quality products will be fine.
    Toolcrafts for the win!!!
     
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    r.tenorio671

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    ...I would suggest if the brand of upper receiver you plan to use also makes BCG's, you use that manufacturer's BCG as their design and manufacturing processes would be consistent with the dimensions of the two parts with interoperability being the goal. The bolt you chose should be one that the barrel manufacturer recommends based on what barrel extension they use on the barrel they produce. E-mail inquiry to the manufactures is your friend ;-)
     
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    JS8588

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    ...I would suggest if the brand of upper receiver you plan to use also makes BCG's, you use that manufacturer's BCG as their design and manufacturing processes would be consistent with the dimensions of the two parts with interoperability being the goal. The bolt you chose should be one that the barrel manufacturer recommends based on what barrel extension they use on the barrel they produce. E-mail inquiry to the manufactures is your friend ;-)

    As it happens, the Lantac UAR is well built & has a nice, tight (though not quite thermal, unlike their side charging uppers) barrel/receiver fit.
     

    Ravenworks

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    Everyone mentioned good products, Toolcraft are just about everywhere.
    Rubber city is local for me and I use their stuff in my big guns.
    Something that you need to think about before buying is spare parts.
    Every product listed in this thread have parts available at many places.
     

    db2000

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    If you can get a headspaced bolt from your barrel maker, go with that option. If not, I've had good luck with SixFiveArms bolt in my Grendel (same bolt for the 6ARC).
    I agree. I tried the best FA LMT they had with .223 Wylie Seekins upper and lower thinking what a great option. It wouldn’t always close completely. Had to use forward assist. Geissele super braided 42 and H2 I believe. I’m a firm believer that Frankenstein mixes, no matter how “great” are asking for trouble. Especially in .308 and derivatives. Stick with the company making the barrel and match it.
     

    Neurotic

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    DSG Arms makes a "supported" tail bolt carrier at a reasonable price. I do tend to think a supported tail ( better centered in the buffer tube ) "could" have long range precision benefits in a properly assm.d AR rifle using a long range cartridge.
    https://dsgarms.com/upper-receiver-parts-dsg-4101-0004

    Using a headspaced bolt with it "should" help precision.

    That looks very similar to the Radian/Alpha/Azimuth enhanced carrier.
     
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    makaug

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    DSG Arms makes a "supported" tail bolt carrier at a reasonable price. I do tend to think a supported tail ( better centered in the buffer tube ) "could" have long range precision benefits in a properly assm.d AR rifle using a long range cartridge.
    https://dsgarms.com/upper-receiver-parts-dsg-4101-0004

    Using a headspaced bolt with it "should" help precision.
    According to Joe Carlos, a "match" bolt carrier (one that doesn't tilt as much) improves group sizes by 8.8%, so your thinking aligns with his research.

     

    JS8588

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    Awaiting more FCD bcgs to drop

    I like FCD's stuff, but there's not a ton of innovation in their BCG. Is it a well made NP3 coated BCG? Yes. Does it do anything for accuracy that a standard BCG won't do? Nope.