Sons of Liberty Armorers Class - AAR

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  • Feb 25, 2006
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    I took the Sons of Liberty Gun Works (SOLGW) Armorer’s Class in Zachary, LA July 30-31. The class was taught by the owner, Mike, and one of his top armorers, Jesse. The class is billed as a top to bottom examination of the AR-15 platform, and it lives up to this. Mike was front and center the majority of the class and impressed me as a genuine expert in the field. Mike goes into the history of the platform, from the very beginning, and makes a real effort to give the student a comprehensive understanding of the system from back to front.

    Day one is the lower, day two is the upper. You can take the class one of three ways – you can build a gun from parts to completion, you can tear an existing rifle all the way down and put it all the way back together, or you can take an existing rifle up and down as far as you see fit, i.e. many people chose to watch barrel / gas tube/ barrel nut / FSB / muzzle device installs as opposed to pulling their upper all the way apart – but it is your option.

    Deciding which rifle to do surgery on was a real internal debate. I settled on my Fauveske. When I was conserving Grendel ammo, the main use was hogs and coyotes in South Texas, and it is what I think of as a classic 16” 5.56 carbine that mainly shoots green tip at nuisance animals. It is a frankengun – the upper is Noveske parts with a switchblock on a fluted Craddock Precision .750 stainless barrel, with a NHR rail Clark Custom Guns cut for the switch and assembled. It wears a 30 cal Thunderbeast Dominus. The results are super excellent, it generally holds sub 2” with green tip and is a sub MOA gun with match ammo. The lower is an early Lancer I built probably a decade ago – I thought it was a good option to see what I could have done better. It came out better than it went in.

    Mike emphasizes the fire control group, bolt carrier group, buffer/spring and gas system are the areas that make or break the gun. The slowest, least interested, most distracted cell phone addicted student comes away aware of the basics - you're creating a hole, filling a hole, and you only use a roll pin once.

    Each area is explored – the specifics of the fire control group, the individual parts in the LPK, the explanation of what mil-spec – “the most bastardized term in all of guns” – means. Mike gets into the metallurgy and why 6061 vs 7075 matters, why you don’t cut a sintered hammer trying to do a kitchen table trigger job and so forth. One neat thing about the class is that in general, if a rifle in the class was deemed to have a substandard part a SOLGW part was given as a replacement. One police department sent folks with Bushmasters and they were nearly half SOLGW parts by weight at the end of class.

    If you take this class and build or tear your rifle down – you’ll leave with a gun that is built right.

    Mike makes the point that heavier buffers with proper tungsten weights cost more, hence many guns carry basic carbine buffers. There is explanation of how we started with a 20” bbl gun using a 5.5 oz buffer – in carbines, the H2 is now the default minimum suggested buffer weight, but everything is based on total configuration. The point is made throughout the course that the gun is an algebra equation – what happens on one side (buffer and spring) must balance on the other side (gas system and bolt mass/speed).

    Day two is about the upper, which you come to realize is about the barrel and the bolt; everything else is support staff. The barrel is the star of the show – everything is built around the barrel. The bolt, on the other hand, does all the work – it removes the brass from the hole and then fills it with a new round every single time you press the trigger. There is extensive discussion about the ejector, extractor and the 10 cent springs in them that make the gun run. Everyone in the class is given SOLGW extractor springs, which are visibly larger and stronger than stock. Everyone is given the opportunity to see if their ejector and spring are up to spec as well. It is heavily emphasized that those two parts and their springs are a huge part of the process. Mike discusses the metallurgy of bolts , 158 Carpenter vs 9130 etc, ad nauseum. If you nerd out over metals and finishes, you’ll be knee deep at least. He discusses the use of finishes on bolt carriers and how some are trash, while others have benefits but might nuke the steel i.e. if you have to get to 900 degrees to apply a finish - that might not be a universal good. Gas keys with nitride finishes were measured to determine which were undersized as a result of not being properly finished. My Noveske passed - they are machining or spec'ing them correctly - but others failed.


    Mike proves some points about the difference between kitchen table guns, shit factory rifles, and top shelf factory rifles. This is summed up in the mating of three parts that are ultimately going to determine how the rifle runs = the fit of the barrel into the upper, and the fit of the gas block onto the barrel. The point is made by the discussion of tolerances and the allowable range – and resulting stacking. SOLGW measures and sorts for out of spec, high side and low side. Mike shows us what a properly sized barrel and gas block interface looks like – he taps it into place with a hammer. Then he shows a barrel that meets spec on the skinny side, and a gas block that is as wide as it can be to pass – and it spins around the barrel like a stripper on a pole. The barrel into upper fit is discussed as well and ultimately it is understood – if you buy parts for a kitchen table gun, you get what you get with regard to parts and how they happen to fit together with regard to tolerance stacking. A well built factory gun allows for the manufacturer to mate parts with the best fit and to put together the best 1000 guns out of a run of 1000 various parts vs the happenstance and hope method.


    One interesting line of discussion with regard to the gas block. Mike has a strong opinion about the best way to attach the gas block – dimpled barrel with a 25 in/lb torque spec. He says he’s seen the “speed bumps” manifest inside the barrel on fine gauges beyond that - it is a thing. Deformation of the bore is also his beef with pinned units – he questions as to whether the stress of pinning may lead to the barrel toward having a pinched point. Clamp on blocks have screws that introduce yet another metal into the expansion equation seen between the block and barrel. Mike suggests either a 4150 barrel with a 4140 block or stainless/stainless for expansion purposes. Aluminum and Ti have significant differences from steel. What I found most interesting was that some higher end manufacturers are apparently going to thread on blocks with a locking nut. That makes all the sense, would minimize blow by and eliminate punching into the bore one way or another.


    Muzzle devices and torque, myths, simple malfs, complex malfs – the list goes on. This class is about 16 hours of a data dump. I’ve built an AR or three prior to this, but I still bought a couple more tools prior to the class to make sure I could go from built to totally stripped to rebuilt. SOLGW sells a $400 tool kit that has everything a boy could need. They say good things about the Real Avid full kit – I had a combo of mainly Wheeler and Real Avid stuff and had zero issues with tools. I am absolutely more confident in my ability to build a better AR than I was before the class.

    I could go on. If you take the class you get the power point in pdf if you bring a thumb drive, and you should bring a notebook as Mike drops a lot of knowledge along the way.

    I came away believing SOLGW is serious about building fighting guns. Mike makes the point that there are fighting guns, competition guns, precision rifles, and pieces of shit built with the expectation they are unlikely to ever shoot any meaningful round count. He says if he were shooting a three gun championship, he’d probably pick up a JP. He’s complimentary of the competition when they’re doing it right and calls out actual examples of problems with the competition when their parts are before you in class and don’t meet spec. The class isn’t a SOL sales pitch outside of Mike demonstrating that the reason they have their basically unlimited warranty is they rarely have to fix anything because they’re built right to begin with. At the end of the class, you’ll understand that Mike has put thought into every – single – part from the origin story at Armalight to where it exists today in various forms and functions.

    If you have the opportunity and interest, I would be surprised if you don’t learn a thing or three in this class. Five stars – I learned a number of things both days.
     

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    He didn't recommend JP per se. His point was that they build a purpose built competition gun, and if the worst thing that happens if it chokes is you don't win a competition - get the gun built specifically for competition. I'm sure people compete with SOLGW rifles, but when you walk out of the class you'll believe their DNA is to build reliable as the first metric - if a gun could shoot softer at the cost of reliability and the range in which it will still operate, they're not going to sacrifice the reliability. You won't find low mass bolts and a SOL gun whereas it is JPs bread and butter.

    Similarly, if you want a precision rifle, there is a different scope of understanding the compromises to accomplish that 1/2 MOA or 1/4 MOA or whatever you're chasing.

    That reminds me - there is a lot of discussion about suppressors, the different types, the state of the art, and how they generally make guns dirty faster and accelerate wear at every part of the process.

    Mike had good things to say about KAC, expressed admiration for John Noveske, likes old Colt 6920s - the companies and guns you'd expect - and gives examples of what good they've done and where he has philosophical disagreements. As an example, Stoner and Noveske were both opposed to subjecting a bolt to a High Pressure Test prior to the Magnetic Particle Imaging because they thought it was needlessly abusive to the bolt - Mike says, what do we expect to learn from the MPI if we didn't HPT? I see both sides of that but tend to agree that the MPI doesn't mean much if it hasn't been stress tested.
     
    I had a good understanding of tolerance stacking and what I think of as margin to failure - i.e. maybe it works, but how far away is it from failing - but this class really hammered home that even buying 100% of the parts from a given manufacturer isn't going to necessarily give you the results you get from a factory gun if it is from a manufacturer that is serious about the art. If you're +/- .001, .002, .003 = that means two parts can range from interference to a .006 gap where you're trying to get a seal.

    If I didn't have every rifle I could hope to have, I would absolutely go into with an unbuilt gun, parts that were all from one manufacturer as possible and desirable, and with some consideration given to the possibility you've confirmed how your barrel fits the upper and that you have a gas block that is snug - if you have to return something or sell extra parts, c'est la vie.

    One thing I found interesting was there were three guys in class that were "operator" types - running short suppressed SOL 308s in helicopters - and they were there in large part to understand what the guns are trying to tell them so that they have diagnostic ability before there are problems. The class hammers that a 20" with a rifle gas/buffer will run soft and sweet indefinitely if you pour oil on the bolt occasionally - but as you add power, chop it up, and add cans - you can go from thousands of trouble free rounds to a couple hundred depending on your equipment, environment, etc.
     
    The class hammers that a 20" with a rifle gas/buffer will run soft and sweet indefinitely if you pour oil on the bolt occasionally - but as you add power, chop it up, and add cans - you can go from thousands of trouble free rounds to a couple hundred depending on your equipment, environment, etc.
    Quoting for posterity.

    -Stan
     
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    I don't know if that is good or bad
    If you're referring to the post above yours, it's good. Iraqgunz (Will Larson) was a well known armorer and trainer who died unexpectedly around 5 years ago. He taught classes similar to SOLGW, and Mike considered Will his mentor and credits the existence of SOLGW to him.
     
    I read your write up with great interest as I am currently building my first AR15. Of particular interest to me as a former machinist is the tolerance stacking of parts. After reading about the fit of the gas block onto the barrel I was curious an measured mine. I bought a Rosco barrel and the non adjustable gas block from their bloodline series. The gas block journal measures .749 and the gas block measures .7495. My question is should I be concerned about this and return the gas block for one with a .749 dimension? Thanks for your advice
     
    I read your write up with great interest as I am currently building my first AR15. Of particular interest to me as a former machinist is the tolerance stacking of parts. After reading about the fit of the gas block onto the barrel I was curious an measured mine. I bought a Rosco barrel and the non adjustable gas block from their bloodline series. The gas block journal measures .749 and the gas block measures .7495. My question is should I be concerned about this and return the gas block for one with a .749 dimension? Thanks for your advice
    No ...it would be an interference fit. If their both the same exact diameter, the gas block won't slide over the gas journal. ...former machinist?
     
    I understand that it would be an interference fit, yet OP mentioned the instructor using a small hammer to install the gas blocks that were unacceptable to him for fit
    No ...it would be an interference fit. If their both the same exact diameter, the gas block won't slide over the gas journal. ...former machinist?
     
    Mike illustrated a good fit as one where he taps it on - not beats it - tap tap tap. Not finger loose slide, not warm up your shoulder.
     
    I read your write up with great interest as I am currently building my first AR15. Of particular interest to me as a former machinist is the tolerance stacking of parts. After reading about the fit of the gas block onto the barrel I was curious an measured mine. I bought a Rosco barrel and the non adjustable gas block from their bloodline series. The gas block journal measures .749 and the gas block measures .7495. My question is should I be concerned about this and return the gas block for one with a .749 dimension? Thanks for your advice
    Former machinist, using rosco parts?
     
    @346ci I’m not a well off as some here obviously are, I read several write ups here and the had not really anything bad to say about Rosco. I know they are not too tier such as CLE, Craddock and Bartlien but they were in my price range, and I am no operator or prs shooter. I am coming to understand what people were saying about this site ☹️
     
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    I understand that part, never had any intention of beating it on with a sledge.
    But I digress I’m out
    You'll likely have no issues with the Roscoe barrel, so long as you temper your precision expectations to the reality of the cost of the barrel. And, an interference fit is not necessary for gas block function. So long as it goes on and doesn't wobble all the way down it should be fine. I have rifles with gas blocks that slipped on with little effort, and rifles with gas blocks that needed some persuasion. Neither have shown to be unreliable.
     
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    @346ci I’m not a well off as some here obviously are, I read several write ups here and the had not really anything bad to say about Rosco. I know they are not too tier such as CLE, Craddock and Bartlien but they were in my price range, and I am no operator or prs shooter. I am coming to understand what people were saying about this site ☹️
    As long as you know the difference, all good.
     
    You'll likely have no issues with the Roscoe barrel, so long as you temper your precision expectations to the reality of the cost of the barrel. And, an interference fit is not necessary for gas block function. So long as it goes on and doesn't wobble all the way down it should be fine. I have rifles with gas blocks that slipped on with little effort, and rifles with gas blocks that needed some persuasion. Neither have shown to be unreliable.
    Thank you for the reply. If I get 1 MOA at 100 yards with proper reloads or match factory ammo, I’ll be happy with that. This rifle will be used for hogs and coyotes out to maybe 300 yards and hopefully not but home defense if necessary.
     
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    The front sights on all M16's are slip fit. While there is an advantage to gas efficiency, a 100% sealed gas block is not a requirement for reliability or long term durability. Higher spring rate gas rings are probably a better solution without incurring the inconvenience of pressed on gas blocks. With that said, even pressed on gas blocks leak unless you go with conical seats and sealed ferules, like KAC. But what does that get you, a reliablerer gas system or just greater cost?
     
    Maybe both. Less gas is like less horsepower. There is no benefit to a bad seal that leaks a bit out either.

    While it isn't a requirement per se, there is no benefit to anything other than 100% of the gas you're supposed to have.

    This site is an amazing technical resource, just have a thick skin, ducks back, and soak in the good parts
    I hear you, that’s why I came back 😂😂
    I figure the best place to learn about this platform was with guys who have slept with their rifles more than I’ll shoot mine in what’s left of my lifetime
     
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    Maybe both. Less gas is like less horsepower. There is no benefit to a bad seal that leaks a bit out either.

    While it isn't a requirement per se, there is no benefit to anything other than 100% of the gas you're supposed to have.

    Prove it. One dude's symposium and an industry outlier isn't indicative that wide scale change is in order for the single most common firearm in the history of the human race.
     
    It's just not necessary to hammer on a gas block...none of mine are hammer on. Just slip fit and they work alot better than the 1 moa build that was discussed.
    Plus most are SA adjustable that bleed off gas, and are totally reliable... And super accurate. Leaking gas on purpose.
    Hammer on sounds like a lot of hot air to me and unwanted in my build.
    You could just blue locktite it on for a better seal, if one thinks its necessary.
    But I don't do that either.
    Example this gas block is a left over that is too large in dia, to fit a reused 308 win 700 factory rifle with 8000 rds on the barrel.
    The 26" police barrel was chopped, profiled, threaded for used barrel entension and muzzle break, gas journal turned, and gas port drilled.
    For $340 this used barrel, home built AR 15 will shoot 1/2" 5 shot groups and works reliably.
    Since I bored it myself, (I am a machinist) I could have made a press fit, but it's unwanted IMO.
    I build accurate ARs, most will shoot 1/2" 5 shot groups, non have a hammer on gas block...most have an adjustable gas block, blowing off gas on purpose ...
    But you go ahead beat your gas blocks on.
    I'll take the 1/2 moa accuracy and not even be concerned about it.
     

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    Prove it. One dude's symposium and an industry outlier isn't indicative that wide scale change is in order for the single most common firearm in the history of the human race.
    I'm not trying to debate that the amount of pressure you signed up for is the amount of gas you want.

    RE: there are bleed off gas blocks - exactly - and they are trying to deliver the amount of gas you want. You could well want more or less based on ammo, cans, specific set up.

    That is the perfect example - if you have a gas block that is bleeding off AND LEAKING you are losing more than intended.

    Wouldn't you prefer parts that fit just so, across the board, particularly if they are under pressure?

    Build yours how you wish. I'll continue to prefer things that fit as well as they can for the intended use. That is my personal preference. If you want a gas block that vents due to loose fit, good luck and God bless.
     
    Maybe both. Less gas is like less horsepower. There is no benefit to a bad seal that leaks a bit out either.

    While it isn't a requirement per se, there is no benefit to anything other than 100% of the gas you're supposed to have.
    Superlative Arms Bleed Off Gas Blocks have entered the chat…
     
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    @346ci I’m not a well off as some here obviously are, I read several write ups here and the had not really anything bad to say about Rosco. I know they are not too tier such as CLE, Craddock and Bartlien but they were in my price range, and I am no operator or prs shooter. I am coming to understand what people were saying about this site ☹️
    One of the problems I’ve seen with some other sites is that people with no or little experience can post ad infinitum to satisfy their twitter-like urge for recognition and validation, when there simply is no real substance to validate.

    So you get dudes with high post counts repeating things they read somewhere from another invalid and inexperienced source, and the whole thing magnifies on itself into tons of noise and very little accurate substance. Without experience, it’s extremely difficult to vet the material, so new and unsuspecting people read the erroneous posts and see large post counts, then perceive that as being valid.

    Same with Youtube videos. I’m seeing more young guys with no/little experience with channels that have good editing and presentation, but they just fluff the time away with trivial or general information, much of it bad. Newer, less-experienced viewers see it and think, “These guys really know what they’re doing!” They program bots to pad the channel comments/hits/engagement as well for sponsors so they can finally have the viewership necessary to get that Sonoran Desert Institute or scrot-shaver shill money.

    Sniper’s Hide has generally avoided that and attracted highly-knowledgeable people, while shunning the amateurs who try to sound authoritative. It has been like that since the 2000s when I first saw the site.

    You could spend years trying to square away some of the other sites, and that self-indulgent urge for a more twitter-like community will always have an extremely high noise-to-signal ratio. The owners of said sites don’t care because it generates more ad revenue for them with sponsors. The money simply out-weighs the importance of accuracy or enforcement of post quality.

    Another thing you’ll see with the Hide is that the quality is generally self-regulated, with occasional intervention by the ownership. So long-time and known experienced shops/barrel makers/shooters/reloaders/competitive shooters will immediately recognize when someone is off-track and try to keep the ship on the right course.

    So the result is that the quality of posts and recommendations here will have a very low noise-to-signal ratio, and the signal will be very strong relative to accurate information, often based on decades of experience in the specific topic.
     
    @346ci I’m not a well off as some here obviously are, I read several write ups here and the had not really anything bad to say about Rosco. I know they are not too tier such as CLE, Craddock and Bartlien but they were in my price range, and I am no operator or prs shooter. I am coming to understand what people were saying about this site ☹️
    Your Rosco will do just fine.

    AERO/BA Barrels are like rolling the dice where you'll lose more often than you'll win (but damnit, their CHF Hanson profile has me wanting to roll...)

    Faxon is paying more for the same as above. At least since Nathan left.

    BCA is a 50/50 shot even though no one likes to admit it. Might even be 70/30 in your favor.

    Rosco...You're probably going to get a shooter. Maybe not .5 MOA. Maybe not even 1 MOA, but probably less than 2 MOA. They make a good, durable barrel that will hit what you're aiming at.
     
    I think if there is some bleed off at the gas block, and the system is functioning just fine, with the combination of gas port size, spring, buffer weight, then it really is of no detriment. My focus would be onto checking if that gas block was secure enough to handle some heat cycles, vibration, and such Murphy antics. So, I can see SOLGW opinion on the matter. (I've sanded and hammer on a bunch of gas blocks onto WOA journals and there was still some soot evident on the barrel in front of the GB on practically all of them)

    I will say I like how SOLGW posts their gas port sizes after their testing. They seem spot on and the only size I have a question on is their stated gas port size for 18" SPR is smaller than most. SOLGW goes sub .100 where WOA goes .108.
     
    Mike illustrated a good fit as one where he taps it on - not beats it - tap tap tap. Not finger loose slide, not warm up your shoulder.
    One of the biggest failure points I’ve seen over the years is when people bring DIY carbines to courses, that slip-fit gas block tends to be a problem if they’re one of the few that’s having reliability issues. The last one I saw slipped forward from carrier key clipping, resulting in single-shot mode.

    TDP-built guns run all day and night, even in the freaking Arctic/Sub-Arctic (to include 11.5”), while many DIY parts-bash ARs crap the bed repeatedly.

    All that stuff on SOTAR is legit when it comes to carrier bore diameters, bolt dims, gas block fitment, gas tube alignment, receiver dims, BCG clearance/travel, firing pin protrusion, extractor springs, extractor geometry, ejector spring/channel clearance/ejector face depth, action spring length, gas port diameter, mag well dims, chamber spec compliance, etc. Most of this can’t be controlled by the DIY-er unless you have bins full of parts and good gauges.

    When I started collecting the Retro stuff, where you look only for original parts, and simultaneously got big into Grendel, it made me realize how many different things were contributing to reliability that I took for granted on Mil-Std guns.

    In the early 2000s, when I started shooting 3-Gun and worked at an FFL that focused on mil/competition shooters, I started seeing Vismod-15s that would crap the bed when subjected to a round count, whereas all the issued M16A1s, M16A2s, M4A1s, and M4s I used ran like champs even with old-school 1970s and 1980s vintage 30rd mags (as long as the magazines were serviceable/not split/dented/bent lips).

    One of the funny things to watch was guys and gals who like to tinker get sucked into the retro world, especially the purists who could only have real parts, then go to the range and say, “Man, this thing runs like a champ. It just feels right." Especially 20” M16A1 kits.
     
    I think if there is some bleed off at the gas block, and the system is functioning just fine, with the combination of gas port size, spring, buffer weight, then it really is of no detriment. My focus would be onto checking if that gas block was secure enough to handle some heat cycles, vibration, and such Murphy antics. So, I can see SOLGW opinion on the matter. (I've sanded and hammer on a bunch of gas blocks onto WOA journals and there was still some soot evident on the barrel in front of the GB on practically all of them)

    I will say I like how SOLGW posts their gas port sizes after their testing. They seem spot on and the only size I have a question on is their stated gas port size for 18" SPR is smaller than most. SOLGW goes sub .100 where WOA goes .108.
    With leaky gas blocks, they will eventually carbon-fill the voids, which then makes the system more efficient at keeping gas contained in the tube and expansion chamber in the BCG, which will often bump up the cyclic rate a little.
     
    The only TDP gas blocks are the various M16 and M4 front sights. All the rest of the gas blocks out there are someone's version of what they think is best. One person thinks cross pinning is "the way" while another thinks cross pinning induces stress and absolutely shouldn't be used. One guys says 100% gas seal is "the way" while another thinks a little leaking is perfectly acceptable.
     
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    The only TDP gas blocks are the various M16 and M4 front sights. All the rest of the gas blocks out there are someone's version of what they think is best. One person thinks cross pinning is "the way" while another thinks cross pinning induces stress and absolutely shouldn't be used. One guys says 100% gas seal is "the way" while another thinks a little leaking is perfectly acceptable.
    You can also add the SOPMOD Block II low profile gas blocks, the SPR PRI gas block, but the principles, dimensions, and materials science are what are important.

    The after-market has to make slip-fit blocks for the DIY-er, otherwise they would see 98-99.x% return rates.

    I really like what ArmaLite did with their SASS gas block, which had a flanged gas tube that was connected to the block and pinched in-place with a lock nut from behind:

    iu


    I also like what KAC did with the Mod 2 gas system:

    iPhoneMarch282014196_zps2ceb59f9.jpg


    KAC Mod 2 has a mechanical approach that seals both ends of the block on the journal, without needing any chemical sealant. It uses a similar brake line plug and tube flare approach used on the ArmaLite Inc. SASS, but looks much smaller and lighter. That is what makes it so easy for an armorer to work on, since the block can be removed when needed, but won’t dislodge for any reason due to the indexing slot, and the forward lock ring that pinches it against the shoulder of the barrel. It’s a very simple, effective, and maintainable design.

    Noveske’s Switchblock has two gas ring sections like a Stoner DI bolt, along the adjustable gas plug that rotates inside of the gas block itself, which has two cylindrical sections-one for the barrel, and one for the plug. The Armalite Inc. SASS gas block also has these two recesses, if you look on the plug.

    US07856917-20101228-D00000.png
     
    I've had great luck with switchblocks. I've gotten away from other adjustables - I had a Superlative that was bad from the factory with a piece of metal shaving in the adjustment, and that made it a single shot when first built. Slowly but surely switching everything else out to the SB or fixed. Thus far, springs and buffers have allowed everything to be tuned without the need for 20 different positions. YMMV.
     
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    If we could go back in time and share decades of notes with Stoner, I think that KAC Mod 2 would be something to really consider.

    Biggest disadvantage with it is the barrel-finishing/profiling process adds the 12 o’clock notch for the shoulder and the lock nut threads on the journal. Not a big deal once it’s added to the machining steps. Eliminates the need for pinning and doesn’t introduce any stresses against the bore from an angle perpendicular to the bore.

    I would have also skipped the .224” bore and gone with something a little larger, but that’s a different conversation.
     
    I've had great luck with switchblocks. I've gotten away from other adjustables - I had a Superlative that was bad from the factory with a piece of metal shaving in the adjustment, and that made it a single shot when first built. Slowly but surely switching everything else out to the SB or fixed. Thus far, springs and buffers have allowed everything to be tuned without the need for 20 different positions. YMMV.
    AR15 barrel with appropriate gas port dia, and yup. These ADJ blocks have come in very handy dealing with the AR10 stuff where most nothing is guaranteed with specs.
     
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    I've had great luck with switchblocks. I've gotten away from other adjustables - I had a Superlative that was bad from the factory with a piece of metal shaving in the adjustment, and that made it a single shot when first built. Slowly but surely switching everything else out to the SB or fixed. Thus far, springs and buffers have allowed everything to be tuned without the need for 20 different positions. YMMV.
    After decades now of people thinking that buffer weight is how you tune the action, I can say that spring weight is far more effective in dealing with cyclic rate.

    For adjustable gas blocks, if I see a set screw, I just pass. I’ve been using the Bootleg Adjustable Gas Carrier for the past 7 years on 4 different builds and it works as advertised. It gets the most use on 12” Grendels suppressed. Love it. So easy to adjust through the port, and you can easily see the ejection pattern change with each adjustment.
     
    The original production Colt Model 601 rifles had a larger gas port and an Edgewater Spring Guide, not the buffer we know today.

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    The original 55gr 5.56x45mm ammunition was loaded with tiny stick propellant, one of which I think was IMR 8208M (precursor to our modern IMR 8208XBR), and those rifles ran beautifully with very clean bore and gas systems. DoD could not get the round counts they were demanding that would pass the MAP, MPLM, and MPSM specs using the tiny stick powders, so surplus ball propellant with lower flame temperature (WC 846) was substituted without consulting the rifle designers. It’s also a slower-burning ball propellant, so the burn curve got extended with higher pressure down-bore.

    That raised port pressure 10,000-20,000psi and caused the cyclic rate to depart from the acceptable window of operation. Changes made to the AR-15 subsequent production models and XM16E1 band-aid uppers was to reduce the gas port diameter and replace the Edgewater Spring Guide with the rifle buffer we still have today.

    Those changes were standardized with the Colt 603 M16A1 and 604 (USAF M16 with no Forward Assist), in addition to chromed bores and chambers, parkerized BCG with chrome bolt bore in the carrier (replaced fully hard-chromed BCGs), forged FSBs, stronger furniture with more glass fill in the phenolic resin plus a cleaning kit compartment, birdcage FH, fully-fenced lower receiver around the mag release button, Forward Assist, and tighter controls placed on parts manufacturing with the updated TDP.

    But they had to spec the rifle around that new ball propellant ammunition, which is often overlooked by those who like to dive into the details of all the other outward-appearance parts.
     
    If we could go back in time and share decades of notes with Stoner, I think that KAC Mod 2 would be something to really consider.

    Biggest disadvantage with it is the barrel-finishing/profiling process adds the 12 o’clock notch for the shoulder and the lock nut threads on the journal. Not a big deal once it’s added to the machining steps. Eliminates the need for pinning and doesn’t introduce any stresses against the bore from an angle perpendicular to the bore.

    I would have also skipped the .224” bore and gone with something a little larger, but that’s a different conversation.

    the kac mod 2 gas system is a very elegant design
     
    After decades now of people thinking that buffer weight is how you tune the action, I can say that spring weight is far more effective in dealing with cyclic rate.

    For adjustable gas blocks, if I see a set screw, I just pass. I’ve been using the Bootleg Adjustable Gas Carrier for the past 7 years on 4 different builds and it works as advertised. It gets the most use on 12” Grendels suppressed. Love it. So easy to adjust through the port, and you can easily see the ejection pattern change with each adjustment.

    the adjustable carriers can make for a very pleasant shooting experience without significant hassle

    i have had mixed results with adjustable gas blocks

    the only downside i have noticed with adjustable carriers is that they to my ears seem to make the noise levels higher at the shooters ear