AR15 Bolt Carrier Group Coatings & Finishes - The Good & Bad

hello and thanks for joining School of the American Rifle today's video is about AR-15 bolt carrier group finishes and Coatings I'm going to share with you throughout my career of what I've seen with different finishes and Coatings I'm going to share with you the good and the bad of different finishes and Coatings and in the end it's up to you to make a decision you can take my advice you can discard it but I'm going to share with you over 20 000 ARS that have crossed my bench in classes what I've seen and let's go ahead and get into it so I sort of have these segregated um you could say it's my favorite to least favorite as we go from right to left there's always exceptions to that rule the purpose of this video is not to disparage companies who make products with these finishes it's just to talk about what I've seen and just to make you aware of it so let's go old school we have our fully Chrome bolt carrier group Chrome will add Dimension to a part so if you make a part the outer Dimension will be larger once it's chromed and the inner dimensional or hole will be smaller once it's groomed so here's an old school Colt 601 boat carrier this is from 1961 this is one of mine there are some different features about these that uh if you have a close eye you could detect it has a fully round carrier key they're only staked in two spots there and there the extractor is sometimes referred to as a full lug instead of it being angled there it's squared off even though it doesn't work as a lug it has a fat firing pin which is not part of the carrier but it's inside there has no Ford assist notches it has a larger opening here but these are features and that really has to do with the Coatings but as you can see sometimes even Chrome can corrode this has corrosion underneath the carrier key inside the carrier key even on the bolt itself if we were to take it apart but generally speaking when it comes to efficiency and that's the main thing that I'm going to talk about when it comes to these Coatings the efficiency of the bulk here so if you haven't seen my previous videos here's a cutaway of an AR-15 bulk here basically it's just sliced in half now when I talk about efficiency what I mean and I have a separate video about this if you want to look at that one it goes into more detail but gas comes in through the carrier K this is the gas tube that interfaces with this comes in here and it pressurizes this area once it pressurizes it your gas rings in relation to the opening here of the gas ring run and the bolt tail in relation to the bolt tail run have to seal gas for this bolt to pressurize it works like a piston and it'll basically blow forward unlock and then the gun will start to cycle if you have worn gas Rings where if this tail is undersized or if the hole that the bolt tail sits in is oversized or the gas ring run is oversized gas will leak and that causes inefficiency in the system generally speaking military guns ones that are made by FN and Colt are very efficient gas systems all the way from the gas block all the way to the inside here on the civilian side completely different ball game there is Dimensions that are all over the place and it's important depending on the ammunition you use the purpose of your gun to have an efficient bulk here because that helps it operate under non-perfect conditions so when I talk about efficiency I want good efficiency I want this to have very little leakage put that off to the side and we're going to get back into these Chrome ones so generally speaking companies who Chrome the bolt carrier group whether it be the bolt the carrier or the carrier key but the bolt carrier group all together when they Chrome it they tend to be efficient now I'm not saying all Chrome bolt carrier groups are efficient and I'm not saying they're always perfect but generally speaking the companies who do Chrome the components try to do a good job for the most part now there is exceptions to that rule I'm going to introduce a more modern Chromebook Care Group of concealing the manufacturers of these because people like to take these videos out of context so this was a quite expensive more modern boat Carrier Group and I made some changes to it and the reason that I made changes is because the company who made this put a carrier key on it that had an oversized bore here which made it inefficient the carrier 3 board on here is actually slightly inefficient on this so I replaced the screws with Ox I've restaked it my carrier key is phosphate and it's Chrome lined the phosphate coating makes it really easy to push the metal to stake the key I replaced the extractor because having a chromed extractor makes it slippery which is not optimal for the purpose of the part so even though I have a Chromebook Hair Group which is mine I've had to make changes to it to make it what I want it to be and it's still not optimal because it has a slightly inefficient three bore inside of it quite an expensive carrier so there's an exception to that rule but I generally like Chrome a lot doesn't mean that it's going to be perfect though you can see on some of these some of these are older ones too this is an older bolt carrier the larger opening here for the retaining pin no forward assist notches but someone along the line decided to replace the old carrier key and they put a nickel boring one on there they didn't stake really good those aren't the right grade screws not optimal at all so just because it Chrome it's chrome doesn't mean that it's good you can see on some of these older Chrome carriers they have these odd staking notches here and then this is like the second generation here none of these do a really good job of holding those screws in place I wouldn't replace these because these are all retro carriers they're original so I'm not going to upgrade them they're good as they sit for the purposes of being a piece of History I'm not going to push these hard and try to make them fail then we move up to phosphate coated bolt carrier groups so these are phosphated on the outside some people say that they went to phosphate over cost I'm not going to get into those types of things what I like about phosphate in relation to Chrome is phosphate tends to hold lubricant really well so this when you lubricate it the lube stays placed better than it does on the Chrome almost always this one's an older one looks like they used an older Chrome to carrier key but the inside of most phosphate bolt carrier groups are chromed if you look inside here you'll see Chrome in here and you'll usually see Chrome in the carrier key I'll get better examples for the shot this is a rather old one more of a collector's piece than one that would be used for a defensive gun here's one that's chromed it's hard to see but that's chromed on the inside and this is what I like to see either Chrome on the entire bolt carrier group or at least Chrome on the inside of it this particular example is what I consider a bad unit though because they're using inferior screws it doesn't have good staking even though it's an efficient carrier if we roll it over on the bottom side of it it's an unshrouded carrier so I'll do a comparison real quick not the back end here not this area here this is an M16 cut AR-15 cut I'm talking about this see how this is cut away this is a modification that colt did I believe starting in the 70s and some companies adopted it some Bushmaster rifles had this some DPMS rifles had it Ruger rifles had a lot of companies played with these unshrouded carriers but basically it was a way to make the gun so it couldn't slam far if you took Parts out of it I do not like to see this in any AR-15 because this causes extra friction which was not part of the original design so even if you have the phosphate coating with the Chrome lining you can still have problems you can have insufficient staking all types of stuff this is a bolt carrier group from a very reputable company some of you you can probably identify who makes them based on different features and that's okay that means you have a good bit of experience but this is a fantastic bolt Care Group very efficient this is Chrome lined in the carrier key and in the bolt sometimes you can see it weeping out on the edges right there see that's the Chrome but this is a fantastic unit this one doesn't have any markings but again some of you may be able to recognize this is it extremely expensive um phosphate and chrome lined one again we'll be able to see on the front we have the Chrome basically weeping out of the edge and the entire bolt on this is chromed so these are both in my first place category the least amount of problems when it comes to the finish the company that the companies who usually produce Chrome to bolt carrier groups or phosphate and chrome line bolt carrier groups tend to pay very particular attention to making sure that the parts are finished properly and of the right Dimension to make them efficient we're going to move further down we have a more modern Chrome to carrier again some of you may be able to recognize this is still in the packaging so I'm not going to crack it open but it has special cuts on the rails here to make it push through fouling and debris a little bit better or sand if you will wink wink some of you guys may know what this is um sometimes these are in the less efficient category even though they're quite pricey but carry group doesn't make them bad it just means that if you use a barrel with a smaller gas port and maybe there's leaks otherwear on the gas system it might not run right with your gun so there's always exceptions to that rule another one that is one of my least problematic finishes is going to be np3 this one isn't marked by the manufacturer but they uh they did their homework fantastic staking good screws if you look at the bolt they put a phosphate extractor on here MP3 is quite slippery so why do you think they would do that because MP3 is slippery and you don't want the extractor to also be slick you want it to grab one to the ammo so companies who tend to do MP3 coatings put a lot of effort into making sure the parts are right before this finish is applied if you look on the inside of this right here it's probably hard to see with the camera but this is extremely rough in here very rough that part is not a surface that you have to worry about let me get the right light not important though inside of here I'm just going to point to it so you can see some people will complain about that not important not only do I care about the dimensions of the inside of the carrier but let me pull my cut away away again I want these dimensions in here to be smooth and if they're rough in this area it can tear up the gas rings if they're rough in this area here can tear up the gas tube flange if it's rough here it can start wearing at the bolt tail so it's not just about the dimensions it's about how those Dimensions were finished before they were coated or treated with something and the companies who do np3 phosphate with chrome or fully Chrome generally pay very close attention to the internal dimensions and the finish of those terminal internal dimensions all right let's move down a little bit further and we have what's referred to as a nano coating I'm going to put these in the same family as what's referred to as DLC we have a DLC carrier here a DLC carrier here and again some of you may be able to recognize who makes these components here's the DLC one here bolts a slightly different design on this one if we look really close to the back of the lugs you can see that there's some pretty aggressive wear already occurring right at the edge that can be an indication that your Barrel extension is not time right in relation to your upper receiver and your boat care but this particular example has some problems generally companies who do DLC it's a a vapor disposition coating from what I understand I might be wrong generally these are more in the middle of the road as far as the efficiency goes they're usually finished very well on the inside of the three bore and companies tend to use pretty good Fasteners and to do a pretty good staking job with these as you can see these are rapidly different designs you guys may be able to identify what kind of carrier this is but generally is the middle of the road when it comes to efficiency some companies like the company who makes this one here they go out of their way to knock coat the extractor they use a special process to manufacture their Carpenter 158 bolt which makes it stronger they have a can pin made of a different alloy which makes it wear less very very good bolt carrier grip you'll probably be able to figure out who makes this one but DLC is generally a pretty consistent coating sometimes it doesn't go all the way inside the three bore it's a vapor coating from what I understand so sometimes you'll see like a rainbow finish on the inside of the carrier and you might think that it's not coated it is it's just not going to be as uniform as the outside so DLC I'll consider that middle of the road and now we're going to go start getting into the things that I really see a lot of issues with and it doesn't mean that if you have this that you're going to have a problem or your gun's going to be dangerous but you might start seeing issues if you look closely so this one is a nitride bolt carrier group it has some different features it has more vents for the bolt carrier so it vents gas a little bit more efficiently they beefed up the tail right here but look right here this is an expensive carrier and I have no doubt the manufacturer who made this would fix this but look at the top of the carry key where they staked it they staked in the wrong place it's supposed to be staked on the side of the screws this one wasn't staked in the right place supposed to be staked here and here they went way too far forward when they staked it so this one is slightly more inefficient than some of these DLC ones it's not staked in the right place not not disparaging the company who made it but this one is less efficient which means if you put it on a gun with a small gas Port it might not cycle right and they mix that they miss that here's a nitride bolt carrier grip that's actually bent it might be hard to see it in the video but this thing has been it won't go into an upper receiver generally speaking when I'm dealing with parts that are nitride and both of these are nitrite I believe suspect that they use a lot of the companies use the same dimensions to machine these openings in here that they would if they were going to Chrome it or code it with something because this is not a coating this is a treatment right so what you usually end up with is a bulk carrier group that has a larger three board Dimension here here here and inside the carrier key which makes it less efficient a lot of companies who use nitrite also use bolts that are made in 9310 which can also become more brittle when they're nitrated depending on the process 9310 has a very narrow heat treat range so if you get it too hot after you've properly heat treated you make it brittle not all companies but some companies who do this nitrating is a more affordable way to coat this bulk Hair Group than the DLC the np3 the phosphate with the Chrome lining and the Chrome so you're going to see more bulk hair groups on the market that are nitrite it doesn't mean that yours is bad doesn't mean yours is inefficient but since it's more cost effective companies tend to dump cheaper products onto the market that might have the nitride finish applied now we're getting into what we refer to as PVD type Coatings which are also from what I understand a vapor type coating we have one here this titanium nitride and another one here that's sort of shiny in my experience once you get into more of the blingy style Coatings stuff that's golden color or extremely shiny they tend to be inefficient and they also tend to have very rough interior three boards they pay a lot of attention to how the outside looks generally speaking and the insides that actually matter they look rough the inside of this one looks like somebody used one of these Dremel sanding drums to finish it but the outside is beautiful this one actually has problems with the bolt face I'll try to get this in camera the bolt face if you look right here it's actually pushing outwards there we go right there it's pushing outwards so the firing pin is trying to blow the opening for the firing pin outwards so the headspace is actually getting shorter on this gun the firing pin on it binds because the bolt is bent the carrier key is misaligned so it binds on the gas tube it's a pretty bold carrier but it's got lots of problems this one is actually from one of the videos that we did a while back one of the worst ones we've ever captured on camera I don't know if this thing's imported it says Made in the USA on it I truly don't know who makes this but it's a terrible character not all boat carrots that are gold in color are going to be bad but that's that's the numbers for me they don't lie and then my least favorite which is probably going to cause the most controversy and it's not intended is going to be in n i b or nickel boron probably one of the worst Coatings ever applied to the AR-15 bolt carrier I'm not alone in this opinion my buddy Mike mahowski from Sun celebrity Gun Works shares the same opinion I'll share with you the most common problems one is the coding that's applied to the bolt we have it on the back of the lugs and we have it on the bolt face when you add a coating to the surface and you don't account for it you end up with short headspace on a lot of guns I would say about one and three one and four bolts in relation to the barrels they're used and have short head space that can cause pressure issues it can cause reliability issues but that's a problem I also see issues with firing pin protrusion so once the bolt locks up the firing pin has to push out to ignite the cartridge the primer specifically if you add surface to this with the coating you have less protrusion sometimes the same thing on the back of the bolt on the tail when you coat this Bolt and you add something there it doesn't stick out as much anymore so I see issues with headspace I see issues with fire and pin protrusion one of the other common things that I see and it depends on how it's coated I don't have one that has the screws that are the same color but let me grab the the MP3 one just to give you an example some people confuse MP3 with this it's not the same let's say you buy a nickel boron bolt Care Group and the screws are the same color as the carry key that means that they did all the assembly they staked it and then they did the nickel bore onto it if that happens there's something in the process whether it's the the nickel boring process or it's whatever they flush it off with I've seen it consistently the the carrier key actually starts to get loose and wiggle or leaks gas because whatever they're using gets stuck in this Gap here and it starts to corrode you'll actually see rust or corrosion underneath the carry cake and gas starts to leak or the carry key gets loose again it leaks if you have this set up here where the screws were installed after things were coated here's what you can run into I have an example here we cannot seat the screws on this because they coated this with nickel boron it filled the threads and now the screws won't see now I could fix this I could tap the holes put the carry key on here but this one was made wrong and the carrot key was loose after they shot it a couple hundred times because this was never torqued down and it didn't clamp the carry key right let me show you with a little cutaway that I made so look the carrier key can't get tight because you can't tighten the screws anymore and you can muscle them in there but you don't quite get that clamp that needs to happen doesn't mean that if yours is nickel boron this is going to happen but this is a common thing that I see going back to the headspace issue this company here you can see that they use a different bolt material this is a phosphate Bolt I suspect they went with that material because at one point they were using nickel boring bolts and they switched over why I suspect because they had dimensional issues with that coding in relation to protrusion and headspace the other thing that I see consistently with nickel boron is what I suspect is some type of chemical reaction if you use a nickel boron a lot you'll notice that they tarnish almost like silver does and what I understand is that there is a really deep valleys and Peaks that occurs with the surface and sometimes the in imperfections get filled with fouling and the the bulk here and the bolt can actually become like a lapping tool so if you do have nickel boron and the company who bought it from says don't use lubricant my advice is use lubricant because it's going to cut down on things embedding into the surface and it's going to allow the bolt carrier to work as it's intended to and not actually wear things down the last thing is going to be in relation to that when these components tend to embed let's say you had a nickel boron bolt like this one stuff gets stuck in the surface here inside of the carrier key and in between the three bore where the gas Rings ride and the gas Rings themselves if you run the gun dry as some people do and you store it with the bolt carrier closed if you ever let it sit with no lubrication and try to charge the gun you usually have to fight the charging handle really hard to get it to go out of battery to cycle now once you break that Bond the gun will start working but if it's a defensive gun something you're storing for use you do not want it to be difficult to charge the weapon so again if you're going to use nickel boron my advice is to lubricate it generously it's going to run better with lubricant on it so from favorite to least this is our order basically Chrome or phosphate with chrome MP3 goes right along with it I'm not going to say that that's less you just don't see that much of it because there's very few companies who produce a bulk carrier group with MP3 don't confuse this with nickel boron and we have DLC a lot of companies who make fantastic bolt carrier grips will use DLC so don't take my advice here as saying don't pick one of these I would still happily run these in my gun but sometimes you need to account for any slight inefficiency of the gas system and the bolt here with what you're trying to do with the gun when it comes to nitride they will raise my eyebrow PVD or tin and then these I won't even use in my guns this is actually a fantastic design the company who makes this if they made this in Chrome I'd be all over it their carry key design is really really ingenious better than the two screw design if you damage the Carrick you basically unscrew it and put a new one in really really neat design but the company who makes this is sort of stuck in their ways when it comes to nickel boron so I don't think they're going to change it if they do I'll have several of my guns if you're not familiar with how I check for efficiency in my previous videos that we make all the time talk about efficiency using this pin gauge set basically looking for efficiency of the carrier we'll put this one here and we'll measure the opening say there measure gas ring run there and then we'll take one of these pins and try to drop it through this little opening here we'll also measure the opening for the carrier Cape this is efficiency checks not good not and not bad efficient efficient mid-range and inefficient inefficiency does not mean the gun won't work and I know I'm repeating myself but some people will literally hear me say something four times in a video and then say hey did you talk about efficiency and I'm like really so um this is my uh this is my advice on all the guns that I've worked on my favorite right underneath my favorite and then this is when you might start getting Into the Danger Zone but not a guarantee as always I hope you found this video educational and thanks for watching

Channel: School of the American Rifle

Views: 106,712

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Id: Yfs1Czm8iiE

Length: 25min 17sec (1517 seconds)

Published: Mon Feb 27 2023