Robinson Armament Early Production M96 Rifle in Detail

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  • Jimbob2.0

    Ultimate Member
    Feb 20, 2008
    16,600
    Seems like Robinson arms is going to start up a limited batch of new m96s, would you recommend this gun over others at $2.5k?
    Kinda tempted since i like how it looks

    See post 9, they are not going to be cheap. Would be shocked if they issue at $2500 in today's market.

    This is a mouth watering thread, there is one sitting on GB right now with some kind of aftermarket underfolder. Neat looking, would prefer something more range functional but shows the flexibility of this platform.
     

    Combloc

    Stop Negassing me!!!!!
    Nov 10, 2010
    7,212
    In a House
    They've been promising more M96's since January of 2020 so it might be a long wait. As it stands now, I would only recommend this rifle as a collectors item unless Robinson begins manufacturing parts again or starts selling what parts they are sitting on. I have not fired this one nor do I ever plan to for fear of parts breakage. To me, it is nothing more than an interesting mechanical oddity and that's exactly why I held out for one with all of the early features. This one was perfect for me because I know it had originally been purchased by a ballistics lab and had just sat unfired since new and remained unmolested or otherwise fiddled with. Some of these seemed to be perfectly reliable and bulletproof while some literally broke the first time out. I think QC on these was obviously lacking but I also get the feeling that the later the rifle was made, the more likely it was going to be trouble free. For actual use, I would recommend any number of rifles over this one.
     

    Jimbob2.0

    Ultimate Member
    Feb 20, 2008
    16,600
    They've been promising more M96's since January of 2020 so it might be a long wait. As it stands now, I would only recommend this rifle as a collectors item unless Robinson begins manufacturing parts again or starts selling what parts they are sitting on. For actual use, I would recommend any number of rifles over this one.

    Definitely agree with that, scarce, parts hard to find. Niche gun for advanced collections and very rare use if at all. Of course a lot of guns are falling into that category either by value, bans or import restrictions!
     

    Combloc

    Stop Negassing me!!!!!
    Nov 10, 2010
    7,212
    In a House
    See post 9, they are not going to be cheap. Would be shocked if they issue at $2500 in today's market.

    This is a mouth watering thread, there is one sitting on GB right now with some kind of aftermarket underfolder. Neat looking, would prefer something more range functional but shows the flexibility of this platform.

    The one you are looking at comes with the top feed setup. If he talked that up in his title and description, it would bring big money. It the right people see it, I can see it selling for over 5K even though it's been slightly messed with.
     

    Combloc

    Stop Negassing me!!!!!
    Nov 10, 2010
    7,212
    In a House
    It's been a bit but, as you are aware I'm sure, life has its own ideas about what you are going to do with your time! Anywho, I'm back at it and we're going to take the handguard off.

    Like thee magazine well, there's not much to it. Just press out the single pin:


    And pull it straight down and off the receiver:

    You might have to rock it front to back a little bit to get it off because it's a tight fit. But a tight fit is a good thing because it means that it doesn't wiggle around when mounted. There are lots of interesting things to see on the receiver in this picture but we'll save all of that for later once we have everything disassembled. For now, we're just focusing on the handguard so hold your horses Francis!


    Looking at the bottom (rear it to the left) we see that the grasping ribs wrap the whole way around:

    The square cutout for the barrel release button is nicely molded and there are several holes running along the bottom. Whether they are meant for cooling or as mounting points for your favorite "tacticool" rail, I do not know. You can also see the mold line running up the middle.


    Flipping it over now to get a look at the inside:

    There are no steel reinforcement bits molded or riveted into the handguard but there are several transverse ribs formed during the molding process that serve as stiffeners. These ribs also form fit the handguard to the receiver ensuring a nice snug fit while allowing cooling air to circulate.
    If you're wondering whether or not it's flimsy, it's not. The plastic is stiff enough that there is minimal flex but not so hard as to be brittle. In short, it does its job just fine.

    The mounting pin passes through just behind the middle reinforcing rib so there is extra plastic in this area to prevent cracking:



    Well, that one was short and sweet. Next time, we'll remove the bolt assembly and see what makes that tick.
     
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    Combloc

    Stop Negassing me!!!!!
    Nov 10, 2010
    7,212
    In a House
    In this post, we're going to remove the bolt group and take a look at it. Let's get started.

    To remove the bolt, we start on the right side of the rifle at the ejection port:

    Currently, the bolt is closed. On many rifles, you simply pull the charging handle to the rear and the bolt group falls out the back of the receiver. With the M96, you first need to disconnect the bolt assembly from the gas piston. How do we do that? Read on my good man.

    On the side of the bolt carrier, we see a little tic-tac shaped thingamadoodad:

    That thingamadoodad is actually a button.....the button we press to disconnect/disassemble the bolt carrier from the gas piston. We will call it the "disassembly button" or simply "button".


    So, using a non-marring tool, press in and hold the button:



    While keeping the button pressed, use the non-marring tool to pull the bolt carrier to the rear a ways:

    It is now free of the gas piston and you can release pressure on the button.


    The bolt group will now fall out the back of the receiver:

    Where in the hecks is the recoil spring?? It's wrapped around the gas piston and we'll see it later. Notice that there is something shiny in the top front corner of the ejection port. That's the rear of the gas piston.


    Before we go pulling it apart, let's take a look at what we've got. We'll start with the right side:

    Front is to the right. The bolt is currently in the unlocked position. Although we can't currently see it, the firing pin spring is pressing against the rear of the bolt. If we were to press on the bolt face, it would move backwards into the bolt carrier and rotate into the locked position. But as soon as we stopped pressing on the bolt head, the firing pin spring would push the bolt forward into the unlocked position again.
    Moving our ever inquizitive gaze rearward, we come to the tic-tac button we pressed in to release the bolt group from the gas piston. Below the button is one of four guide lugs/rails (two per side of the carrier) that runs in a slot formed as part of the receiver pressing.
    Directly above the button is a little shiny bit. This is a roll pin that holds the disassembly button and its spring in place.
    The cavity above the roll pin is necessary for fitment of the disassembly button. That will make more sense when we look at the front of the carrier in detail later.
    Directly behind the roll pin is a long oval area machined into the carrier. While this could probably be considered a lightening cut, it's main purpose is to allow the roll pin to be removed or inserted should you need to service the disassembly button.
    Continuing to the rear, we come to a little circle near the rear of the carrier. This is a pin that is removed to disassemble the entire bolt assembly.
    Below the pin is another guide rail. The rear of this guide rail is where the bolt carrier ends. Everything to the rear of the rail is not part of the carrier but is a removable "tail" that holds the firing pin and its spring in place. If I'm understanding this thing correctly, it's also supposed to act as a sort of built in safety to ensure that the rifle will not fire out of battery. This part caused some problems and underwent two design changes but that's beyond the scope of this article. We'll look at that part when we disassemble everything. But be aware, the general consensus is that this first pattern tail may not do it's job with regards to safety and RA offered to upgrade it for free when they were still supporting this rifle.


    Here's the left side of the bolt assembly:

    Rear is to the right and that's where we will start. Some of this is going to be redundant but I'm going to type it anyways just in case some of you are as daft as I am and need to have everything spelled out.
    We first have the removable "tail".
    Moving forward, we again come to one of the guide rails with the head of the disassembly pin above it.
    As we continue moving forward, the next thing we come to is the camming slot and cam pin. Currently the bolt is in the unlocked position. When the rifle is assembled and ready to fire, the cam pin would be at the rear of the camming slot. When we finish with this picture, I'll use two more pictures to illustrate what I am talking about.
    Below the cam pin is the fourth guide rail/lug.
    Above the guide pin is another tic-tac shaped cutout. Inside we can see the lug that locks the bolt assembly to the gas piston. This lug is machined as part of the disassembly button. So, as you're pressing the disassembly button from the right side, you're pressing the lug part of the button into the cutout on the left side of the carrier and out of engagement with the gas piston. Make sense?? I hope so because that's as well as I can explain it without removing the part and I'm not doing that.
    The last thing we come to is the bolt sticking out the front of the carrier. Again, it's shown in unlocked position.


    So, here we see the bolt in the unlocked position with the cam pin at the front of the camming slot:


    And now the bolt in the locked position with the cam pin at the rear of the slot:


    In the above, I'm assuming that the reader has a basic understanding of how a typical rotating bolt design works. If all of this talk about "locked" and "unlocked" has you scratching your head, I suggest that you truck on over to wikipedia and type in "rotating bolt" to start your journey down the rabbit hole. If you're at all interested in mechanical design, I guarantee it's a fun and fascinating rabbit hole to explore!!


    A bottom view of the bolt assembly:

    Not much to see here. The four guide rails/lugs are quite obvious. Where the bolt carrier ends and the removable tail begins is clearly evident too.


    Top view:

    The numbers "396" are the last three digits of the serial number. They appear to be some kind of paint and while they may have been put there by Robinson, I've never seen this before so I must assume that they were applied by the ballistics lab for some unknown reason.


    Front view of the carrier illustrating the roll pin which holds the disassembly button in place:

    All of the marks you see are from lockup with the barrel extension.


    Front of bolt:

    Note six locking lugs (seven if you count the little one on the extractor). Also of interest is the ejector slot cut at the 5 o'clock position. This is not an AR folks.


    The last picture before we disassemble all of this is a detail shot of the tail and the rear of the spring loaded firing pin:
     
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    Combloc

    Stop Negassing me!!!!!
    Nov 10, 2010
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    Now that we've taken a general look at the bolt assembly, let's take it apart.

    We start with this pin found on the right rear of the bolt carrier:



    Using a bullet point or some other non-marring tool push it out from right to left:



    Once the pin is out, the tail that retains the firing pin will come right off, exposing the rear of the firing pin:

    Notice that the pin fits only one way.

    Now pull the firing pin out:



    The spring is a friction fit on the firing pin but pulls off easily if desired:



    Here's a detail shot of the tail piece showing the machined divot the retaining pin passes through:

    This is the first version that came on the rifle. It's purpose is twofold. It retains the firing pin in the bolt assembly and it is supposed to keep the rifle from firing out of battery by preventing the hammer from contacting the firing pin unless the bolt is fully forward. However, apparently, more than one sold rifle did, in fact, fire out of battery, severely damaging it. As a result, this part was redesigned twice and Robinson Armament would replace your earlier version at no charge. I've done a lot of research on this matter and it seems to me that the the real problem lies not with this tail, but rather with the barrel retention system. We'll look at that in some detail when we get to barrel removal and replacement but for now, I'll give you the short and sweet version. Simply put, if your barrel isn't properly seated in the trunnion, the bolt will not fully lock into the barrel extension and the results can be a catastrophic kaboom. If you practice reasonable diligence when replacing the barrel, it shouldn't matter which type of tail is on your bolt carrier.


    A closeup of the firing pin:

    I don't know if this is stainless or chromed. One of you folks who is more knowledgeable than me will know.


    Continuing with disassembly, we next remove the cam pin:

    There is no special place it needs to be in the cam slot for removal. Note the hole in it for the firing pin to pass through.


    Once the cam pin has been removed, the bolt will easily pull out the front of the bolt carrier:




    Here's a closeup of the cam pin in situ:

    Notice that it's a little chewed up on its face. I've got a pretty good feeling it's not supposed to be that way.


    For this picture, we've removed the bolt and cam pin from the bolt carrier and reassembled them:

    Notice that the face of the cam pin is not flat. Rather, it has a small tongue projecting out along the bottom face. When reassembling everything, this tongue must be at the 6 o'clock position or the rifle will not go back together.


    Here, we've flipped the bolt over to see the bottom of the cam pin:

    We can clearly see that the tongue has actually started to roll under. Remember that this rifle has been fired very, very little if at all since leaving the manufacturer so this should not be. I think it's safe to say that this part is not properly hardened. Now, to be fair, I don't think this tongue being battered really matters all that much but still, it's not right.


    One last look at the bottom of the cam pin. This time removed from the bolt:

    You can see a shiny area behind the tongue. This is wear from it moving in the cam slot. i don't plan on ever shooting this rifle but I did, I would keep a very close eye on this part and probably have a new one fabricated if it showed any further deformation.


    This picture of the bolt well illustrates the two bands that ride inside the bolt carrier bore:

    These are machined as part of the bolt and they are shiny because the finish has worn off. You don't want the entire length of the bolt rubbing inside the bolt carrier. That much surface contact would inhibit reliability because it would be too much friction and you also need some clearance for debris to collect.
    The circle forward of the front band is the extractor retaining pin.


    The ejector clearance slot:



    And the bolt face:



    The cam pin rests in a blind hole:



    We're not finished with the bolt assembly yet but it's time to wrap up this installment. Rest assured, we will continue in the next post.
     
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    Combloc

    Stop Negassing me!!!!!
    Nov 10, 2010
    7,212
    In a House
    In this post, we'll continue with, and finish up, our study of the bolt assembly.

    To remove the extractor, push its retaining pin out:

    Mine seems to only fit one way. Whether this is by design or specific to this rifle, I do not know. You'll figure it out when you remove yours.


    Once you remove the pin, the extractor and extractor spring lift right out:


    A detail photo of the pin showing that it is thicker in the middle than on the ends:



    Extractor:



    Extractor spring with insert:

    This spring is larger on one end. That end goes in the extractor. I don't know if the insert is factory original or not.


    Here, we see the front of the bolt carrier with the bolt removed:

    Between the lower hole where the bolt fits and the upper hole where the gas piston/operating rod fits, is a small roll pin. This pin holds the disassembly button in place.
    In the upper hole, you can see the part of the disassembly button that engages with the notch in the operating rod and locks the bolt assembly to it. In this next picture, you can see the disassembly button spring:



    Earlier, I mentioned that the main reason for the long oval area machined into the right side of the bolt carrier is to access the disassembly button roll pin should you need to remove it for any reason. Below is a detail shot showing what I was talking about. Without the machined recess, the only way to remove the roll pin would be to drill it out and that would be no bueno:



    Here is the entire bolt assembly disassembled:

    The only things we haven't removed are the disassembly button retaining roll pin, the disassembly button, and the disassembly button spring.
    To some of you older dudes, all of this might look familiar. If it does look familiar but you can't quite put your finger on it, then you need to get your old AR-180 buddy out of the safe more often because you've clearly forgotten how much FUN that rifle is at the range. For you guys who immediately recognized what this is copied from, you're on the ball! If you have no idea at all what the hecks I'm blathering on about, go find yourself an AR-180 and study it carefully because MANY of today's most successful military and sporting rifles are direct descendants of that most underappreciated rifle. For comparison, here is a an exploded view picture of the AR-180 bolt assembly:

    Other than the tail piece, it's pretty much identical in design. Now, that's not to say that the M96 as a whole is based on the AR-180. In fact, the two rifles couldn't be any more different in many respects. To cite just one of many examples, the M96 utilizes a long stroke gas system whereas the AR-180 uses a short stroke system. But with regards to bolt design and operation, they share the same blood. Many people call the M96 a "Stoner 63 clone" but the reality is that it's essentially an amalgam of the AR-180 (bolt assembly), AR70/SIG550 (gas system and driving spring), and the Stoner 63 (overall assembly/disassembly). The fire control system is loosely based on the Stoner too and Robinson also threw in some of their own ideas.....some good and some not so good. We'll look at the Stoner similarities and differences more closely when we compare the two side by side but for now, we'll just say that yes, RA was trying to make you think "Stoner 63" when you look at the M96. However, even a casual comparison of the two will quickly reveal that you got ripped off if you thought you were buying a "Stoner 63 clone". It might look like one if you're drunk at 3AM but what you wake up to the next morning is not going to be what you thought you had last night. Still, it has personality and it's neat in it's own right so you did alright in the end.


    We're done with the bolt assembly for now but there is one thing I need to point when reattaching it to the operating rod. After sliding it into the back of the receiver, you need to again press the disassembly button to fit it over the end of the operating rod. Once you've done this, you may notice that the disassembly button did not pop back out:

    This means that the bolt is not properly mated to the operating rod. This is not a problem. Simply reach over to the charging handle on the left side of the receiver and pull back on it a bit. The button will pop out and let you know that it's now properly linked up with the op rod:



    And with that, we are finished with the bolt assembly for now. Next up, I plan to bore you to death with barrel removal and gas system disassembly. YaY!!
     
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    Combloc

    Stop Negassing me!!!!!
    Nov 10, 2010
    7,212
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    It's been way longer than I had planned but I'm back with barrel removal and gas system disassembly. Removing the barrel is a snap but replacing it must be done meticulously or else you will have a potentially dangerous situation when firing.

    The first step it to remove the barrel. Before we begin, we need to first look at a couple of things. We'll start by looking at the gap between the gas block and the gas tube when the barrel is properly seated:

    Notice that there is an ever so slight gap between the front of the gas tube and the rear of the gas block. This is normal. The space between the two is taken up by a tube that extends rearward from the gas block and fits into the front of the gas tube. This was redesigned on later rifles but that's beyond the scope of this article. I will say that you can retrofit the newer design to these older rifles but the parts must be changed out as a complete set (barrel, gas tube, and piston/op rod).

    This picture shows the barrel release button in what I will call the "locked" position:

    By "locked", I mean that the barrel retaining pin is fully seated in the barrel extension and the barrel is properly locked into the trunnion. Got it? Good! If not, it'll make sense when you see it taken apart.


    Here, I have removed the hand guard so that we can get a better look at the release button in the locked position:

    Notice that the face of the button is generally parallel with the bottom of the receiver. In this position, you can be sure that the barrel retaining pin is properly and fully engaged with the barrel extension. Personally, I recommend that you remove the hand guard before firing to inspect this because if the retaining pin is not fully engaged with the barrel extension, your barrel may, at best, fall out of the trunnion when firing the rifle. At worst, the bolt will not properly lock into the barrel extension, creating a potentially DEADLY situation upon firing. When we install the barrel, we'll cover what an improperly seated barrel looks like.

    SO, to remove the barrel, you first lock the bolt assembly to the rear or remove it entirely.
    Then, you simply press the release button in as far as it will go:

    Then, while keeping the button depressed, grasp the barrel in front of the gas block and pull it forward and free of the trunnion. The barrel is a precision fit in the trunnion so it might not want to budge. If this is the case, you may twist SLIGHTLY as you pull it forward but DO NOT ROCK IT SIDE TO SIDE. Once the barrel is free of the trunnion, you may relax pressure on the release button.

    Barrel removed:




    We have already looked at many of the barrel assembly features earlier so we are not going to cover all of that again. Instead, we are going to look at the few things we weren't able to see when it was mounted.
    Earlier, I mentioned the tube extending rearward from the gas block. Here is a detail shot of that tube:

    There isn't much to see really. It's just a tube. I can't tell whether it is a separate part permanently attached to the gas block or was machined as part of the gas block. Your guess is as good as mine. It's not a tight fit in the gas tube but it it does what it was designed to do. Namely, to deliver all available gas, minus that which was bled off by the gas adjustment valve, to the face of the piston.


    This is the barrel extension:

    It serves three purposes.
    First, it serves as the mating surface for the bolt. After the locking lugs on the bolt pass through the crenellated rear of the extension and the bolt meets the rear of the barrel, the bolt carrier continues forward. As the bolt carrier nears the end of its forward travel, the cam slot acts upon the cam pin, rotating the bolt slightly and, in the process, aligning the lugs on the bolt with the teeth on the the extension. The action is now locked.
    The extension's second purpose is to serve as the feed ramps for the rounds as they leave the magazine. There are two feed ramps because the rifle employs a double stack magazine, i.e. one round feeds from the right side of the magazine and the next feeds from the left and so on. The feed ramps can be seen above at the 5 and 7 o'clock positions.
    The other job the extension does is acting as the mating surface between the barrel and trunnion and to act as the "docking port" for the barrel retaining pin as shown below:

    There are three things of note in this picture. At the front of the extension is a raised ring. It serves as a limiter, keeping the barrel from being inserted too far into the trunnion. I assume it also provides that much more stability when the barrel is mounted.
    The next thing to note is the loss of finish. As stated previously, the extension is aprecision fit in the trunnion. The more precision, the less rock, the more accuracy. The precision fit is the reason for the finish loss.
    The last thing of note is the hole bored in the extension. This is where the barrel retaining pin fits. It too is a precision fit for safety, stability, and accuracy.
    These last two things noted are why it is imperative that you only slightly twist (if necessary) and NEVER ROCK the barrel when removing it. Rocking it can and will abnormally wear the mating parts, destroying the precision fit. At best, it will affect accuracy. At worst, it may render the rifle unsafe to fire.


    THIS IS IMPORTANT ------> If instead of removing it entirely, you have chosen to lock the bolt assembly to the rear for barrel removal, NEVER EVER allow the bolt to fly home with the barrel removed. This is a good way to SEVERELY damage your operating rod. If, for any reason, you wish to return the bolt assembly to the forward position with the barrel removed, GENTLY ride it forward using the charging handle. To ensure that no damage is done to the rifle, I recommend removing the bolt assembly each and every time you wish to remove the barrel.


    To reinstall the barrel, ensure that the bolt assembly is either locked to the rear or removed from the rifle entirely. Then, press and hold the barrel release button. While keeping the button depressed, insert the barrel into the front of the receiver and push it home, twisting it slightly if need be, until it is fully seated. As with removal, DO NOT ROCK THE BARREL DURING REINSTALLATION.

    HUGELY IMPORTANT ----> MAKE SURE THE BARREL RELEASE BUTTON IS IN THE PROPER POSITION. FAILURE TO DO SO MAY RESULT IN RIFLE DAMAGE OR DEATH!!!!
    Let's look at that.
    Here, I have reinstalled the barrel:

    Looks good right?

    The gap between the gas block and gas tube is fine:

    I can pull on the barrel and it doesn't move. Everything looks good to go right? WRONG!!! The barrel is NOT properly locked into position. How do I know??

    Look very closely at the barrel release button:

    Remember when I said earlier that the face of the release button should run generally parallel with the bottom of the receiver? Well, that button is NOT parallel with the bottom of the receiver. This means that the barrel retaining pin is either barely engaged with the barrel extension or, worse yet, not engaged at all. If you were to fire the rifle with the button in this position, I can guarantee you that, because the locking lugs on the bolt are either barely engaged with the teeth in the extension or not engaged at all, you are going to have anything from damage to the bolt and extension to the rifle firing completely out of battery. The result will be anything from destruction of your rifle to death. Sounds fun huh?

    Here is what the barrel release button looks like with an improperly seated barrel, hand guard installed:



    OK.....so the barrel is not properly seated. How do you rectify this issue? It's pretty simple really. The shoulder at the front of the barrel extension keeps the barrel from seating too deeply in the trunnion. So, is the gap between the rear of the gas block and the front of the gas tube correct? If not, the barrel needs to be pushed in farther. If the gap is correct and the button is still not in the locked position, the barrel assembly is twisted in the trunnion. While watching the disassembly button, slowly twist the barrel assembly one way or the other. You'll know when it's right because the disassembly button will pop out into the locked position. You are now good to go. I recommend that you always remove the hand guard when reinstalling the barrel so that you can get the best possible look at what's going on with the button. After you've fiddled with it a few times, you'll learn by watching the button when locking pin is not engaged with the barrel extension at all, only partially engaged, and when it's full engaged. The moral of this story is........... PAY ATENTION TO WHAT YOU ARE DOING WHEN REINSTALLING THE BARREL. YOUR LIFE MAY DEPEND ON IT.

    Before we move on to gas tube removal, I'd like to share my thoughts on the barrel retention system. I don't consider it a "flaw" with the design per se, but I certainly don't think it's idiot proof either. It was copied (somewhat crudely as we will see later) from the Stoner 63 so it is a proven design. The fact is, you can improperly seat the barrel on that rifle too. You just have to pay attention to what you are doing. If you're slipshod in your work, you're going to pay for it one way or another. But then, isn't that true with pretty much everything in life? In the end, YOU have to take responsibility for YOUR actions and use DUE DILIGENCE when putting YOUR rifle back together. Safety starts with YOU. The reality is, you don't need to remove the barrel unless you are cleaning the gas system and you don't really need to do that very often. While I would clean the barrel after every range trip, the gas system should easily go 1000 rounds between cleaning unless you are using corrosive ammunition; something I'm not sure even exists in 5.56mm/.223.


    Alrighty, that wraps up the barrel for now. We're moving on.
     
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    Combloc

    Stop Negassing me!!!!!
    Nov 10, 2010
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    Once we've removed the barrel, the gas tube is next.

    Looking from the bottom, we see the gas tube projecting out from the front of the receiver:



    Looking closer, we find a round lug on the gas tube behind the steel block welded into the front end of receiver:



    To remove the gas tube, simply grasp the knurling at the front of the tube and twist until the round lug is aligned with the slot in the steel block:

    It's a bit hard to twist because it's a tight friction fit at the rear where it fits into trunnion.

    Then pull the gas tube forward until it comes free of the trunnion. You may have to twist slightly as you pull:

    As with removing the barrel, it's OK to twist a little as you pull but DO NOT ROCK as you pull. Rocking is a good way to bend the tube and/or egg out the trunnion.

    Once it's free of the trunnion, pull it out the front of the receiver for cleaning or inspection:

    When reinstalling the gas tube, you may have to twist it a bit as you push it home. This is normal. Also, the trunnion is bored out in such a way that it's impossible for the gas tube to be pushed in too far. Once it's seated in the trunnion, twist the gas tube in either direction until it stops and make sure that the lug on the tube is behind the steel block at the front of the receiver. Done.


    Here's a slightly better picture of just the gas tube:

    I'm not sure whether this part is made of stainless steel or not. Starting from the front at the left of frame, the first hole we come to is one of the gas vent holes. There are four of them but only one is visible in this shot.
    The next thing we encounter is the retaining lug. The distance from this lug to the rear of the tube is precise so that there is no front to back play when it's installed in the receiver. Maybe mine is unique but I don't think so because I've encountered no reports of play in my research so I'm assuming mine is typical.
    Near the rear of the gas tube are two inline holes. I'm not certain of their function but my guess is that they prevent pneumatic pressure as the operating rod and its accompanying recoil spring cycle back and forth.


    The last thing I want to point out on the gas tube is this closeup of the retaining lug:

    As far as I can tell, this is not simply welded to the tube. Rather, the tube wall was drilled through before a peg was inserted and welded in place. I couldn't get a good picture looking down the inside of the tube but there appears to be evidence of clean up inside where this lug is. If I'm right about this, it's a good thing because the peg method makes the whole thing that much more sturdy. It also makes sense from a manufacturing point of view because I think it would be easier to get precise lug placement using a predrilled hole.
     
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    Combloc

    Stop Negassing me!!!!!
    Nov 10, 2010
    7,212
    In a House
    After removal of the barrel and gas tube, we complete disassembly of the gas system by removing the gas piston/operating rod assembly. But before we do that, I want to look at how the assembly interacts with the charging handle and explain why you must NEVER pull back on the charging handle and let it fly home without the rifle fully assembled.
    We start with a picture looking up into the bottom of the receiver after having removed the bolt assembly and barrel:

    The silver bit is the rear of the operating rod (referred to as the op rod going forward) at rest. However, this picture doesn't help us much in explaining anything. All it's really showing is what you will see when you look up into the bottom of the receiver.

    To see what's really going on here, we need to push the op rod to the rear a little bit. We have done that in the picture below:

    Let me explain what you are looking at.
    The notch cut into the the op rod near its rear is what's grabbed by the lug on the disassembly button in the bolt carrier. Pushing the button on the right side of the bolt carrier disengages the lug from this notch and decouples the carrier from the op rod.
    Forward of this notch are two roll pins sticking out the side of the op rod. The rearmost pin runs into the front face of the bolt carrier upon reassembly and prevents over insertion of the op rod into the bolt carrier. The forward pin is used to charge the rifle. In fact, it is shown in contact with a lug protruding out the back of the charging handle. It is important to understand that this pin is in no way attached to the charging handle because the rifle has a nonreciprocating charging handle.
    Remember that the recoil spring is part of the gas piston/op rod assembly.
    Knowing these things, it should now be clear why you must never charge the rifle unless it is fully assembled. When the rifle is assembled and the mechanism is allowed to run home, the inertia created by the drive spring is transferred into the relatively heavy steel barrel and trunnion with the bolt assembly acting as a sort of damper. But without the barrel and bolt assembly in place, ALL of that inertia is transferred into that little roll pin when the mechanism comes to rest. How many times to you think that can happen without the roll pin become mangled and shearing off? This setup was later redesigned and the roll pins replaced with a lug welded to the op rod but the later manual still advised against charging the rifle unless the barrel is installed. This setup is one of the weakest points of this design but it's really a nonissue if you have educated yourself about the rifle BEFORE mucking about with it. Things like this are why I'm a big believer in reading the manual before picking up your firearm.


    ALrighy. With that warning out of the way, I'll now explain how to remove the gas piston/op rod assembly. It's really simple.
    First, push the gas piston to the rear until the forward roll pin on the op rod is disengaged from the protrusion on the charging handle. The position show below is more than sufficient:



    Next, rotate the assembly either clockwise or counterclockwise 90 degrees until the pins are pointing at the top of the receiver:




    Ease the assembly forward until you no longer feel pressure from the drive spring and remove it from the front of the receiver:




    Now that it's out, we'll look at it in some detail.
    At the front of the assembly is the chromed gas piston:



    It's held onto the op rod by a roll pin:

    The piston could have been machined as part of the op rod I guess but I think part of the idea in doing it this way was to allow a bit of articulation to reduce stress on the assembly as it reciprocates.


    A detail photo of the piston head:



    The rear of the op rod showing the already talked about notch and roll pins:


    The brass ring between the drive spring and the forward roll pin rests against the front of the trunnion when assembled.


    In this picture, we see the op rod at the point of initial insertion into the bolt carrier:



    And here, the op rod has been coupled with the bolt carrier, illustrating the the rear pin on the op rod resting against the front face of the bolt carrier:



    Coupled op rod and bolt carrier as seen from the right side:



    While looking at the various parts of the gas system employed on the M96, it may have reminded you of something you've seen before. If so, you memory has served you well! In fact, it's derived from that used on both the Beretta AR70 and SIG 55X series of rifles and both of those designs are based on an earlier system designed jointly by Beretta and SIG before going their own ways....but that's beyond the scope of this article.
    Still, just for the fun of it, here is the M96 compared to a SIG 551:

    It should be pointed out that we are considering only the gas system here and not the locking system. The M96, as we have seen, has a locking system based on the AR-180 while the 551 is based on the AK-47
    On the 551, the op rod is connected to the bolt carrier by way of the reciprocating charging handle but the two systems are very similar otherwise. Both have a removeable gas full length gas tube, both employ a long stroke system where the op rod can be easily disassembled from the bolt group and both have their drive spring mounted around the op rod instead of the more traditional placement behind the bolt group. Stuff like this absolutely fascinates me and it's a large reason why I collect firearms.


    SO that's it for this installment. In the next, we'll take a detailed look at the receiver. Later, I'll go over some cleaning suggestions and we'll finish up by comparing the M96 to a Stoner 63. Until then, enjoy the summer. It's been a hot one here, just the way I like it!
     

    gelmir

    Member
    Dec 5, 2013
    1
    Well Done!

    Would it be possible to get this in PDF format? You did a great job. I've got 2 of these rifles that I've had for years NIB. You've done more for the M96 than Robinson has done in the last 10 years. Bravo my friend absolute bravo!
     

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