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My target grade AR-15 upper build project has been a drawn-out process — I think the wife and I could have made another human being from scratch by now. I’ve finally settled on a bolt carrier group. Pictured above: my affordable, no-frills BCG from Linkin Armory. Despite a shipped-to-your-door price of $139.99, it’s packed with every high-end part and feature you could hope for, all from/done/made domestically. The who’s who list of features is sure to impress . . .

From Linkin Armory’s BCG product page:

Bolt – Carpenter 158 Steel, Shot Peened,each and every bolt is HPT per MIL-C-70599A and MPI per MIL-l-6868, Marked HP MP
Extractor – Upgraded 4340 Tool Steel (vs typical 4140, milspec allows for either per original TDP PAGE 7), Shot Peened
Extractor Retaining Pin – S7 Tool Steel, Shot Peened
Extractor Spring – 5 Coil Cryogenic Processed A401 Chrome Silicone Wire Stock, Black Milspec Insert And Crane O-ring (comes assembled with spring and insert, o-ring included separately)
Ejector – S7 Tool Steel, Shot Peened
Ejector Spring – Cryogenic Processed A401 Chrome Silicone Wire Stock
Gas Rings – Milspec Stainless Steel per original TDP PAGE 6
Carrier – 8620 Steel, Full Auto Profile, Chrome Lined Bore
Gas Key – 4130 Chromoly Steel, Permatex Sealant Applied, Grade 8 Fasteners, Properly Staked, Chrome Lined
Cam Pin – 4340 Chromoly Steel, Dry Film Lubricant Applied Per Milspec
Firing Pin – 8640 Steel, Hard Chrome Plated
Firing Pin Retaining Pin – 1038 Carbon Steel
•Any other specs mentioned or outlined in this list can be read by clicking on The Original TDP.
•All material and processes are Certified and from, or performed in, the great United States Of America.

If I ever finish this build project, expect a review on the BCG another couple months and 500 to 1,000 rounds after that. This summer, hopefully.

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    • The components on the posted one are a little higher grades of steel, as is with the Bolt itself. Other than that, not a damn thing.

      • Yes, many of the components are made of higher grades of material. More specs are hit for things like chrome lining and high pressure testing and materials (e.g. 9310 steel for the bolt does not meet Mil-Spec. It’s easier to procure and machine than C158, and nearly as strong but not quite as it does fatigue more easily, and it isn’t actual spec if that matters).

        Ultimately it may not make a difference, but my ‘smith is going to be matching this bolt face and lugs to the barrel extension for utmost accuracy, and the quality of the bolt and the machining was important to me. Linkin appears to be finishing it to a high degree and to nice tolerances and once my bolt is matched to my barrel I don’t want to have to replace it.

        • You’ll have to enlighten me why your “‘smith is going to be matching this bolt face and lugs to the barrel extension for utmost accuracy” when the AR-15 bolt is already free floating so it can self-center?

    • Unlesd I missed it, the other bolt carrier isnt HP tested, and no info on the springs used.

      But congratulations for missing the obvious changes AND being a jerk about it.

    • This one will allow you to impress the girls with tats and face hardware at the local 3-gun range.

      When you’re comparing BCG’s with some guy who bought one of the low-rent plain-jane versions, you can start rattling off all these specs in a game of “who is more tacti-kewl?”, which you’ll win because you’ll be able to spew more jargon and ASTM/AISI numbers. So that fine looking gal will be going home with you in your Hummer instead of his mere Jeep CJ.

      See how this works?

      • Being able to rely on your gun and know that its going to fire after a couple thousand rounds the same as when you got it is obviously important…….although there are people out there that argue that point and try to just pawn it off as advertising or being a geardo or whatever??? Im sure they drive the most basic F-150 w no upgrades or power sterring cause their just that cool!! Congrats on that boys… Thanks for the pearls of wisdom but I will stick to the linkin armory bcg I used the hell outta mine and it has never failed me and I doubt it ever will!

    • 9310 bolt vs. 158 carpenter steel
      4130 extractor vs.4340
      Not HPT vs. HPT
      Standard 4 coil extractor spring and standard ejector spring vs. 5 coil silicone wire stock extractor spring and silicone wire stock ejector spring

      Those are just the specs that AIM lists to compare with. Hope this helps

        • To be fair, all of the competition makes all of the same claims. Right? We’re comparing all of this stuff in the first place because all of these same stats are on the other companies’ pages also. Everyone’s picking up chicks. This one picked me up because its stats are better than their stats. How else could a consumer possibly compare a bunch of products that look physically identical but actually aren’t?

        • My best suggestion is, if you don’t understand, then any bcg will be fine for your skill set. If I can try to put this into perspective…This particular spec was tested and trusted by varsity players in Afghanistan between August and January this year. Not impressive or irregular as most top tier equipment is tested this way. It is important, however, because not one member of that team would trust their life or the life of their brothers to a $99 bcg from AIM. With that said, there is a growing number of consumers who feel that it is their duty to protect their home and family with the same reliability. Guaranteed function under extreme duty costs more. Linkin Armory can easily offer a standard milspec bcg from microbest or toolcraft for $99 (which is where 90% of these come from) and may consider that in the future. I don’t need a dewalt cordless for my honey-do list, but I bought one ???

  1. Why not add racing stripes while they’re at it? Somehow BCGs manage to survive tens of thousands of rounds without the extra nonsense and expense that this one has. How many millions of these have been tested in actual use? I dunno, I’d rather just buy something I know will work for under $100 instead of untested buzzwords for an “affordable” 50% more.

    My $.02

  2. I suspect that those features have indeed been tested. I went full Nick on my BCG and even got the shiny coating.

  3. So, it’s an “affordable” milspec phosphate BCG which is $20 more expensive than my nickel-teflon/NP3 coated BCG from DS Arms, and as others have said, 50% more expensive as some of the cheaper options on the market, ex. a good $50 more expensive than a black nitrided AIM Surplus BCG, etc.

  4. I have plenty of milspec and one high end Bcg. The high end is a Larue Bcg. The machining quality is amazing. I have never had any Bcg fail me, 4 builds so far. I think in terms of realibility a high end Bcg does not offer much more than a mil spec until you get into the 10,000 plus round count. But when you are trying to squeeze ever drop of accuracy out of your rifle a top shelf Bcg helps.

    • Haha fine, fine. It appears to have some similar specs w/ the PSA Premium one. Is it ever in stock? They’re all out of stock now, and the last time I was on there was a few months ago and they were also out of stock. I know sometimes they blow them out for like $70 but sometimes they’re prices higher than this Linkin one. Of course, it’s easy to sell things really cheap if you don’t actually have any 😛 …I have seen a lot of complaints on the machining like burrs on the bolt lugs and cam channels out of spec. I have a couple cheap BCGs as backups or “investments” for the next legislative scare, but I wanted to go with something simple (i.e. Mil-Spec and no fancy crap) but high quality, from materials to machining. This one looks very nice, but I’ll know more about the machining quality once my gunsmith gets to the fitting process.

      • If your gunsmith is going to hand fit the bcg to the barrel/upper anyway, what differences do burrs on the bolt lugs make? He would simply take those off during the fitting process.

        • That’s true. But the extra time spent on it might cost more than the price difference we’re talking about. Look, there are cheaper options out there but I think they’re cheaper, not just less expensive. I went with this BCG because I think it just might be as good as anything on the market for materials, build, and machining, but at a lower price. Not lower than the cheapest ones out there, but lower than what I felt were potential equivalents.

          That is, excluding really trick units with internally-adjustable gas systems (Gemtech, 2A Armament), interesting modified bolt heads (like Sharps’ reliabolt), and various coatings and treatments. For whatever reason, I wanted to stick with simple and effectively Mil-Spec, yet manufactured/machined with care and with high quality materials like the uber springs and nice grades of steel being used here.

  5. All my bolts and bolt carriers are Low Mass jobbies from JP enterprises (other than their 9mm bolt). I pay more, but I’m ok with that. regularly runs great sales on them (30% off).

      • Dude! Don’t you even operate operationally? A low-mass BCG allows you to put more mass into your tacti-kewl eyewear. Gotta look fashionable, and a low-mass BCG helps you distribute the mass from your BCG into your fashion accessories!

        I mean, come on!

      • Less reciprocating mass can mean less gun movement (staying on target better). Less power is required to cycle it, too, so you can direct less gas back into the action and possibly run a lighter recoil spring as well. To take advantage of a lighter carrier, though, you really do need an adjustable gas block and need to be willing to spend some time tuning everything. It’s a popular option for competitive shooters (3-gun style stuff) who want to tune to a specific ammo and want to reduce recoil as much as possible by reducing moving mass and reducing how hard the gas cycles the system. It can also cycle faster. The “full-auto” profile carrier is heavier because that extra mass (more inertia) reduces the cyclic rate. I don’t really care for this purpose, but some will claim that the heavier carrier with a standard power recoil spring help it slam home into battery more reliably, especially if everything is gunked up or if the lug/lug recess fit is particularly snug.

        • I think even a target ar could benefit. Lower recoil makes it easier to spot your impacts.

          All my ars are for 3 gun. Tuning is easy. Shoot single round, did it lock back, if no open gas more. Repeat till lock back and then a skootch more. Job done

  6. Well, there are some issues in their descriptions of the steels they’re using.

    Starting with 4340 isn’t a tool steel.

    Then I kinda wonder why they’re using S7 in the ejector, but not the firing pin.

    A bunch of choices here that make me go “Whaaa?”

    • And the box it came in probably had a 4-color glossy picture of a ‘hot babe’ in a seductive pose while fondling it…

      • Came in a plastic tube 😛

        It’s my impression that they went with the best components possible while remaining within Colt’s TDP (within Mil-Spec). That may not allow for use of a different steel for the firing pin, for example, whereas maybe it doesn’t specify for the ejector so they went with what they felt was the best possible choice. Admittedly it would be a slightly odd way to go about things rather than just building it out of whatever an engineer would deem the best possible (although I’m sure that would be $$$$$), but it fit what I was looking for, which was a “normal” BCG built to a high quality level.

        • See, this is where I rear up on my hind legs and start into one of my “I’m going to revert to being an engineer” rants.

          The Mil-Spec’s and Colt TDP are what came about as a result of contract negotiations for prices for a delivered unit (with Colt scheming how to maximize their profits) and the military trying to formulate what the lowest bidder would be held to for performance.

          That’s nice contract negotiation, but it bears little in the way of resemblance to engineering a truly superior product.

          Want to engineer a truly superior BCG? Toss the adherence to “mil-spec” this/that and the Colt TDP out the window. Look at the actual requirements of the issue and build something that wildly exceeds the physical requirements in the rifle itself.

          This is what drives me positively nuts about the fetishization of “mil-spec” in the gun market today. The military isn’t setting the standard for “what is best.” No, they’re setting the standard for “what is the least we will accept that a contractor must deliver in order to get paid…”

          I should know. I started my career in a defense contractor shop in comm gear. Could we have shipped better radios? Hell yes. There was all kinds of neat new technology appearing in the comm device market. We could have made backpack radios much lighter and smaller than what we were shipping. To all you guys who humped backpack radios in the 80’s – hope you liked the exercise guys. Sorry you have blown out knees now, but hey, the radios were mil-spec.

          Were we going to deliver something significantly better than mil-spec? Nope. Because there’s scant chance of winning a bid for more money than the lowest conforming bidder once you meet the mil-spec’s. If you exceed the spec’s at the lowest common bid price, OK, that might help you win the bid. But make something truly superior?


        • Agreed. It’s making the best possible thing you can while intentionally choosing to do so within arbitrary confines that tie one hand behind your back. It’s choosing, not being forced, to stay within specific limitations that don’t actually apply to you. It’s weird. However, people also view things like Mil-Spec as the best possible within a given price range and/or as good as makes sense without being excessive. It’s a metric that says XYZ is good enough for military use. Going beyond that can be seen as wasteful extravagance. I don’t need sodium-filled Inconel exhaust valves in my Nissan Pathfinder, even if those are the best possible valves you could build. it would just be a waste. So building something within a spec like Mil-Spec, yet with the best machining and closest tolerances and best materials and processes possible within that spec, can make some amount of sense. I think that’s what they did here. That’s what I was shopping for, at any rate — the “norm,” but done well.

      • Depends. Do you want to run them dry, or are you willing to use some oil/CLP?

        If you’re running them wet, the standard “mil-spec” AR-15 BCG’s work just fine.

        If you’re going to run them dry, then look into one of those that are nitrided help resist abrasion from grit & dust, which are the best reasons for running the gun dry.

        As an engineer turned gunsmith, this fetishization over “this” or “that” specialized steel, specialized coating, etc, etc, etc… is just… I don’t know what the single word is that would properly encapsulate my amused frustration and bewilderment.

        The standard parts work, and have worked for decades now. One’s mind reels at the thought of how much spec-manship there would be if a Garand were the nominal military arm in today’s spec-manship marketing environment. We’d had oprods made premium Unbendium-123, heat treated in legendary caves by wizened gunsmithing gnomes, bolts made of kryptonite on CNC machines with ISO-9000 certification, milled with tools that meet Mil-Spec 87655, stocks made of heaven-only-knows-what plastics/composites that resist flame, cold, water and personal sex lubricants, etc.

        100 years ago, they were heat treating Springfield 1903’s by eye, and while some of those were burned to steel failure, most of them survive to this day. The ones from the the 20’s onwards were heat treated in an oven with a pyrometer, and they used the bog-standard alloy steel of the day in the receivers and bolts (something akin to 4140) and those rifles are 90+ years old, still shooting well. Garands used something akin to 8620 for the receiver and bolt, case hardened an in atmosphere furnace, and they shoot well and have held up to far worse abuse than 99.999% of the AR’s in today’s market will ever see.

        Aside from reloading errors, bore obstructions, etc – I’ve yet to see an AR’s BCG fail. It is a sound design, built for both low cost manufacturing and ease of field maintenance.

        Having been on many ranges in the last, oh, 15 years since the AR craze really took off, I’d really recommend people to invest the money in ammo and shooting lessons over some doo-dad that they really don’t need. A replacement trigger on an AR? That’s a good use of money. A better barrel? Sure, once you shoot out the one you got, unless it started as a real POS. Better fitting stock? Maybe. Better sights? Maybe, if you’re getting older and need them. The AR irons are good, and better are available.

        After that, I start getting really hard pressed to recommend how to spend money on an AR.

        I was talking with a couple of Marines this week (you know, the guys who still believe that everyone in their branch of the military should know how to shoot a rifle well? Those guys) and we were talking about marksmanship. They were justly proud of making expert with their clapped-out weapons at what are ranges far beyond where most AR shooters can hit something the size of a car. With iron sights, issue triggers (which are POS triggers, IMO), and issue ammo. We got to talking about AR doodads… and these guys just laughed. They wished they had a rifle in the Corps half as nice as what they can buy in the AR market today for $1K.

        And these two young men shot expert.

        The BCG is soooo far down on the list of issues on an AR, it boggles my mind that there are so many of them out there in the market.

        • Ehhh, my go-to AR is off the shelf with no modifications other than trigger upgrade. If I’m going to build one from the ground up, I’m going to choose each item specifically. If that means the BCG costs $50 more than a foreign made almost certainly functional but rough around the edges unit but half the cost of the newest shiny amazeballs thing out there, I’m doing it. Not that I scoured the market searching every single possibility out there, but from the time I did spend shopping around this unit appeared to be the highest possible quality without getting into frills, bells & whistles, etc, while at a lower or even much lower price than some of the brand names that cost extra just for the logo.

        • I’m a big fan of nitriding myself, so that makes sense.

          I am an engineer myself (currently studying for my masters) so I understand where you are coming from, but as a non government personnel we have to pay for our parts ourselves, so unlike in the military bolt longevity is an issue. Many of these parts are built with the intention (I think) of using them for the life of the gun, which in theory can be over 20k rounds. That is a lot of ifs and buts and maybes but in the end everyone wants the best they can get for their money and I have yet to think of a scenario where a bolt is too strong, other than the idea that you’ll have to have similarly strong locking surfaces on the barrel or those will fail instead of the bolt.

          Or I could be completely off base and these companies are selling the metallurgical equivalent of snake oil. I’m hoping for the former.

        • As usual I agree with you, DG.
          Re: materials. Failures of 7.62 X 39 bolts has prompted some work on stronger bolts.
          I am not convinced C158 is the best steel for this application.Toughness and impact resistance are probably among the top characteristics required. A stainless tool steel might be appropriate here, maybe A286. (I am aware of some “enhanced’ bolts made of 17-4). Precise machining, deburring, fillet radii, surface treatment (shotpeen), proper heat treating, stress relieving and NDT will add confidence. Properly applied plating/coating/nitriding etc. to finish up. Address tolerances, fitting at assy, mating surfaces etc.
          That should get you a pretty tough bolt.
          Similar attention to each detail part, as well as the entire assembly, should pay off.
          Note the law of diminishing returns may apply.

          Let me know if anybody markets a run-dry BCG.
          For now, I’m using a top-secret proprietary blend of CLP and 3 in One.

      • Eh, not really.

        Tool steels are specifically:

        1. Capable of being hardened to Rc 58+, which you can do with even 4340.
        2. Have “hot hardness,” whereby the steel is alloyed to prevent it from losing hardness when used as a tool and suffering from heating.
        3. They hold an edge really well under high impact/load/heat conditions.

        The edge/hot-hardness issue is where 4340 starts losing.

        4340 is an alloy steel (the “43” indicates Nickel-Chrome-Moly family of alloys) with 40 points of carbon (the “40” means 0.40% carbon). Most tool steels will have 0.60% or more carbon to increase hardness.

        4340 is a great steel, don’t misunderstand, but it isn’t really a tool steel. It is one of the first “superalloy” steels.

        I get to see lots of 4340 in this area. It is used in the big machine shops here in Wyoming for building/re-building parts on the big mining machines. It machines well with carbide, is very strong compared to other, cheaper alloy steels, and easily obtained. Every now and again, I get scraps of it.

        The one downside of 4340 is that you have to do pre/post heating if you want to weld on it.

        • The COC states the RC is at the top of the 4340 range at 60. As to your other two requirements, can you point me in a literary direction to substantiate the claim that 4340 can NOT meet those requirements. Thank you.

  7. I have a White Oak BCG in my White Oak Varmint, two Bravo Company’s BCG in both Bravo uppers, an AIM surplus in a PSA build, and a PSA spare. All seem to work exactly the same. The White Oak is not the auto version but came with the upper.

  8. This thread reminds me of why I’ve never made the plunge into the AR world, and why my life might be better for it… I think I’d like to have an AR, but I don’t have the energy to invest in learning what a “Black Milspec Insert” is or why it’s better than the other (I’m assuming) two dozens kinds and colors of “inserts” available. When I show up at the range with my military surplus rifles and lever guns, I never have to have a conversation about what grade of steel the firing pins are, or what kind of cryo treatment the springs have had.

    • Or . . . you could just get an off-the-shelf fully assembled rifle and enjoy that. Not all ARs need to be built. Heck, I’m still rocking my Bushmaster AR I bought 17+ years ago (EM15 E2S V Match carbine, IIRC). Certainly not top of the line but plenty fun for plinking. Still has the same Aimpoint Comp M red dot I put on it way back then, too.

      I bought and and enjoyed it as is. Never did get into the whole modification craze, mostly as I like to keep my rifles lean and clean without a lot of extra stuff on them. So I look at the current AR market a bit bewildered. Intrigued but bewildered. It does has me thinking about building / assembling my own but there are other guns that interest me instead of adding a second AR.

    • Honestly, just go get a decent stock AR, and leave it be. It really doesn’t need all this heat treated, ionized, nickel plated, spit polished, turd washed, acid dropped, sillyness. If you take all that time, effort, and money all the geardo’s put into that nonesense, and invest it in ammo and range time, you’ll be out shooting those bling boys in a month.

      • That’s pretty much my thinking. At some point, I’ll buy one of the better-regarded “cheap” ARs and spend the savings on ammo learning to shoot it well. Honestly, the only thing keeping me from doing that today, while prices are low, is my reluctance to get into yet another caliber. I’ve got too many ammo cans in the closet as it is. But I know I’ll kick myself if prices run back up and I didn’t take advantage, so I’ll probably do it sooner rather than later.

    • You can find so many choices in the AR market today for $600 to $1000, you never need to worry about the crazy specmanship game. If you have an issue with some part of your rifle later on, you can replace it.

  9. There are two kinds of people who want to buy AR’s. Those who want to be AR owners and those who want to be AR users. AR owners will never know what they have or don’t have because it will never fail them shooting a couple mags on the weekend. This product is intended for serious users doing serious work or serious play. If you don’t understand the difference between this bcg and the PSA, then you don’t NEED it. Any bcg will be fine for you.

      • And those who understand and appreciate the necessity for guaranteed function and reliability. You get what you pay for doesn’t only apply to your underwear, stinkeye?

  10. Making another human being from scratch really doesn’t take that long. I just hope my teenage son doesn’t find that out the hard (easy) way.

  11. I’ve seen a lot of the types of people in this thread standing on the rifle stage at 3gun cleaning oil off their glasses and clearing double feeds (while the clock is ticking) from their bog-standard mil-spec frankenrifles they built from on-sale blem parts and chewing gum with a duct-taped-on (non-adjustable) gas block sight while they try to prove a point. Guess what – they succeeded. “I don’t need no GOTD-dammed JP silent spring cryo barrel/matched bolt Armageddon trigger or proof research stuff ‘cuz I kin built a match-grade special purpose tack-driving laser beam rail gun with fifty cents, a trip to the junkyard, some 250 grit sandpaper and some paracord – in 4 hours. And if anything goes wrong, it’s gotta be the ammo.
    PS – Jeremy S, I like that BCG. Also check out V7 and JP, tho. Haters gonna hate!

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