Been interested in trying a piston AR out for some time now, and since I've been building for some time, a retrofit kit, particularly the Superlative Arms kit, was right up my alley, and I finally managed to get one, but I have a few, simple, some may find "stupid" questions as well, but still would appreciate honest answers to any of the questions. Don't feel obligated to answer all of them, I'll be happy with one at a time. I'm also leaving out the reasons I'm asking the questions out to save on text, feel free to ask though. Thanks in advance everyone!!!

1. Removal of the gas rings on the bolt, necessary or optional? I get they aren't needed for obvious reasons.
2. Rounded cam pins, necessary or optional?
3. Op-rods, are they the same length as gas tubes, both of the same gas system of course(i.e. mid-length op-rod and mid-length gas tube: /=)?
4. It takes more gas to operate a piston system versus a standard DI system? True, false, or kinda but...
5. Carrier tilt, how to diagnose/avoid?

I haven't yet installed the piston kit, for reasons, which is why I'm asking some if the questions, I'm guessing if I had built and used it already I would only have a question or 2 versus 5. Thanks again though in advance!!!

1.  remove the gas rings
2.  not necessary, roller cam pin would be better option.
3.  op rods are not necessarily the same exact length as the gas tube, although they use the same naming convention for gas-port location, depends on mfr design.
4.  I've only found the "more gas to operate" to be true for 7.62x39. YMMV.
5.  you'll see scuff marks at the lower front of the buffer tube.  generously grease the entrance to the buffer tube so that the bolt carrier can glide lubed into the buffer tube, especially the bottom portion. use bolt carrier that has larger back end, use buffer tubes that extend further forward than the buffer detent.  e.g. POF, or Aero Enhanced buffer tube.

i've only used the AA system, not the SA.  YMMV.

Thank you very much!!! I was kinda hoping I could leave the gas rings, as I installed the one piece gas rings on most my bolts, and I'm having some trouble getting it off, LoL.

As far as the cam pin goes, I was looking at getting a Lantac roller cam pin, but glad to know NOT having it won't hold me up(not that I'm in any hurry).

Correlation between the gas tube and op-rod size is a detail I still would like clarified, if anyone can shed some light on that(from my one size comparison, my mid-length gas tube was roughly ⅝" longer than my mid-length gas tube). I plan on  creating another post here to elaborate as to the WHY of this question.

Very curious in regards to your statement on the piston not needing more gas except on 7.62x39 chambered systems, makes sense being a lower pressure round, hopefully someone with experience with the Superlative Arms kit will chime in and say the same thing. Again, this will be elaborated on when I create a new topic after I feel this one has sufficiently answered my questions

I've already got a buffer tube like the one you mentioned, however, this doesn't require the buffer retainer pin to be present to reap the benefits, does it? I removed mine due to the PITA they are when removing the JP SCS, but if I need the buffer retainer, I could pick up the modified JP one that doesn't interfere with the spaces on the SCS. Also, I don't much have a choice in carriers, unless someone makes a gas key replacement specifically for a piston op-rod, which would be awesome, because I'm a big fan of some of the "enhanced" carriers out there with the flared carrier tails.

Appreciate your answer though, really an awesome first response!!! Anyone else have anything to add or build on what rpoL98 said would be welcome.

Attached File

I a believer of anti-tilt buffers over anti tilt tubes.
I make my own, and have no idea where to find one the correct weight for your application.
Most. like Slash's, you have to pull both receiver pins to open up the weapon.
I use a domed buffer, that will open & close with the pivot pin in place, as it cams the buffer back.



The 'dome' is a titanium button head cap screw, that was re-profiled a little.

op rod length will be determined by the piston manufacturers PROPRIETARY design of the interface with the gas block at the front end, and the interface with the "tombstone" on the bolt carrier.  it's a PROPRIETARY adaptation to the AR-15 gas system.

Adams Arms used to offer a bolt-on tombstone to replace the gas key on your bolt carrier, not sure if that was as reliable or durable as the integral tombstone, constantly getting whacked by the op rod., and it's no longer listed on the website anyways.

leaving the gas-rings in provides an unnecessary drag on the system, maybe not much (unless they're totally worn out), but it's still there, contributing to the force needed to close the bolt.  Also the same drag acting when the op rod has to pop the bolt carrier back.  could make a difference in a marginally gassed situation, or when you switch to a weaker-brand ammo.

Sorry, I haven't replied in a while, life got a little hectic, projects came up, completed, and some were scrapped in my time away, but back on project, full swing. I thank y'all for commenting and providing valuable advice/info/insight/feedback that I do truly value and appreciate.

I meant my mid-length gas tube was roughly ⅝" longer than my mid-length op-rod. In the sentence before that I did mention specifically that I was comparing the size of the gas tube to the op-rod, but that's my bad all the way, LoL. Although I could be mistaken and it's the other way around, but that's beyond the point now.

ANYWAYS, before I do something I can't undo, I'd like to find out from anyone who owns and uses or used to own/operate a Superlative Arms piston kit. When sitting idle, does the op-rod sit in the little rounded pocket on the carrier, so that it basically pushes the carrier when a round is fired, or is there some space between them and it impacts and then pushes the carrier back? I'm pretty sure its the first, but want to be sure.

Only other question I currently can think of is a rounded cam pin necessary, or will any 'ol cam pin work? I've got a FCD/SOTAR nitrided cam pin I'm going to use for now, until my Lantac dome-head cam pin comes in, just curious if it's necessary or just a nice thing to have.

Thanks again everyone for your help, I've been excited about this piston retrofit for some time, only wish I didn't do things the hard way, but that's half the fun to me and where I learn the most 😉

For the sup arms kit
1. Leave them if you want. They have no effect on operation. I've never removed them.
2. Standard cam pins are fine
3. The op rods are basically the same length.
4. You're overthinking this.
5. Not an issue. The sup arms kit has its own carrier. There is no carrier tilt.

It's literally a drop in kit. Any standard ar bolt parts will work. I think I use bootleg bolts/parts kits in two of mine. The other is an adams arms bolt/kit from when I converted it

I'll add something else.
6. The sup arms kit comes with a little spring that gets installed on the op rod. Remove it. It breaks and serves no purpose. I asked them about it and they said they started using it because people would complain about the little bit of free movement in the op rod.
7. The bushing that is installed in the upper may not fit. Don't force it. I've only used it in two of the 6 of these I've installed.



Carrier tilt is an older issue from the heavier systems of yesteryear. This bolt operates much more close to how the "piston" on a DI system operates.

You are wayyy over thinking this my man.

There should be a very small amount of play in the op rod when the bolt is closed.  Very small.  Enough to tell that it's not bound up, so you should be able to spin it in place but it shouldn't move front to back much at all.  Whether it pushes or impacts depends on if you use the included spring.  The spring pushes the op rod forward toward the muzzle.  So there will be a very small (thousandths of an inch) gap between the op rod and the carrier "cup".  There will be some impact.  Without the spring, it's more about which way the rod ends up after lock up.  Sometimes it will be resting in the cup, sometimes not, but you'll never know the difference.  Follow the instructions from Superlative and it will be set right.

I have a roller cam pin in one of my pistons (the Superlative one) and the rest have normal cam pins.  Does it matter?  Not even a little bit.  The cam pin will slowly wear a very short rounded groove in the upper receiver until it reaches a point where it stops wearing anymore.  The amount is so minor it's irrelevant.  To be honest, I'm not even sure it's a "nice thing to have" because I honestly can't see why it's a benefit to have the roller cam over a normal cam.

Awesome replyy friend, thank you very much for the info, it's just what I needed!!! If the circumstances were normal, this project would've been much more straightforward, but I'll reveal why all this info-seeking on something the installation instructions provided with the kit should've been sufficient. The reason I didn't just put it out there initially is there are those individuals on here who criticize and ridicule folks like me who stray from the path of average and like to play outside the status quo.

My project was, obviously, installing a Superlative Arms retrofit piston system on one of my current favorites. The variable here that made it not-so straightforward is my barrel is an 11.5" Rosco K9 barrel which utilizes ⁿwhat they call a "patrol-length" gas system, which is longer than carbine-length and shorter than a mid-length system. So being there's no such thing as a patrol-length op-rod, I had my work cut out for me, as I only had one mid-length op-rod to utilize for this project, so I had to get it right the first time, which I'm fairly confident I've got it right, just have yet to take it for a test drive. Of course I'll update when I am able to put some rounds through it!!!

Again, I'd like to thank everyone who took the time to help a brotha out, I doubt I'd of been able to complete this project without all if y'alls valuable insight and first-hand knowledge. I'll attach a link to a pic, figure y'all deserve that much, LoL.

A Pic, I'll take more later

You could measure the gas tube run and get another gp rod which you could grind down the op rod and play with it.

The only thing I would say as a caution that not sure how hard the new contact surface area of the op rod is going to be.  It might be still hard enough for the punishment or starts mushroom after few hundred rounds. Bit that is my take of the solution.

But you make a very good point.  I'm not sure how Superlative does it, but a lot of these systems they harden the very end surface of the op rod, but not the whole rod.  If the whole rod is hardened, it becomes brittle. So only the impact surface is needed.  If you grind that off, you might want to consider re-hardening the end.

OP, I remember seeing a video serious, maybe on YouTube, where a guy was trying to adapt a hybrid Superlative/Adams Arms system and ran into a similar issue.  As I recall he wanted to use the Superlative op rod with an Adams Arms lightweight carrier.  Superlative has a recessed cup in the carrier impact area where AA is flat.  So he had to shorten the op rod.  Not sure if he was ever successful and it's a really old video.  Maybe I'll see if I can dredge it back up.

In the meantime, AP2020 Outdoors has a BUNCH of really useful videos on the Superlative system.  He's an ARFCOM'er too.

https://www.youtube.com/watch?v=0yY1zukbZvo

1: gas rings are really an unknown. Some vendors send complete piston guns with gas rings, some don't. LWRC, when asked by my work, stated the DI bolt sent with the guns was to ensure those parts could be used in a standard M4 if needed. While a thoughtful gesture, it really means that the gas rings are not necessary for their guns at least.

2: rounded cam pins are a solution in search of a priblem and cause a problem all their own. I had one installed in an HK upper and after 5k or so rounds the roller dented the inside of the cam pin track in the softer aluminum  upper because it lessened surface contace area and hard vs. soft material equals damage to soft. removed it and never looked back. It also never made a difference to function.

3: op rods depend on the manufacturer and are generally not  inter system compatible. as for length compared to di gas tubes, no. Not even close.

4: takes less gas. Gas ports on pistons are traditionally smaller and the system is more efficient. At least in complete build systems with proper engineering. After market kits are forced to work with DI gassing (port sizes) and are thusly less than ideal. They require more venting and are generally a shit idea. Sorry, bro.

5: carrier tilt is an interesting beast. Some people experience it bad, and some not.  The tilt not only effects the rear of the carrier down, but also brings the front up. Or  at least changes the angle of attack.  A good piston system with sleds on the rear of the carrier coupled with an extended buffer tube that cups that creates pre-operation contact with the carrier handles this issue best. POF actually makes a good "lipped" buffer tube for this.

Except that the particular aftermarket piston kit the OP has is the Superlative Arms kit.  Probably the best adjustable gas block (piston or DI) you can run if you like fine tuning.  Which means you can tune the gas pressure to the rifle as needed and make it operate the way you want.  It's not just a restriction adjustable, it actually allows you to restrict or bleed off gas.  For the first section of the adjusting, you're restricting the gas to the piston chamber.  For the second section (after full gas) it's venting excess gas forward of the piston chamber which reduces the pressure used.  That makes it incredibly tunable to your personal desired outcome.  It also has something like 48 setting points so you can vent or restrict as you see fit and fine tune it if that's what you want.

The AA system is a restriction based adjustable.  It doesn't vent at the piston chamber, but it does allow you to reduce the pressure in the piston chamber the same way a factory tuned option would.  The venting that happens on the AA system is once the op rod has reached full extension it vents to stop the action.  But that's what all pistons do.  It's also the same thing a "DI" gun does once the carrier reaches full extension from the bolt.  It just vents in a different location.

Those are the only two piston kits I'm very familiar with, so I can't speak to any other.  

Doesn't matter who makes it. Shoe horning a piston system into a pre-existing design is less than ideal.  This has been proven time and time again. Hell, even some ground up designs have failed miserably due to o oversights or plain laziness. See the 6940p.

Attempting to oversimplify the differences between di and piston does not help the OP. These things aren't simple as the track record of many AR piston designs has proven. The proper engineering must take place and the vast majority of drop in piston designs show little actual engineering input from mechanicall to material. There's a reason  no drop in unit has ever been fielded by a .mil unit and only one AR piston design has any long term credibility for operational use.  There are a few others trying to develop that pedigree, but they still have a ways to go.

This idiotic parroting needs to stop. It's cool if you don't like/agree with piston ar's. Either answer the op directing or get out of a tech thread

Derp.

Care to factually counter anything i've said along with your complete ignoring the fact that i did answer the OP's questions?

And perhaps you've missed the part where i'm perhaps the biggest advocate of piston guns (properly built, that is) on this site?

You wouldn't have a personal bone to pick with me, would you?  That's the only reason i could see for such a retarded post.

OK, but... a system not being fielded by a .mil unit is not exactly the standard you want to use here.  .mil is not the gold standard for pretty much anything and anyone who has dealt with .gov contracts knows that.  Also, OP already has the kit.  None of the rest of the discussion is relevant.

No personal bone to pick. The DI system was never a good system-we just invested so much time into its development that it functions really well now. It's tiresome seeing people parrot incorrect information. This site is especially bad about it.
*edit*
I came off rude and I shouldn't have-i saw this before I had caffeine and get tired of people saying things based off only having experience with those heavy ass sig Pistons of yester year. I shouldn't have lumped you into that

Apology accepted, and thank you.

I would ask what you consider incorrect about what i said?

I would also assert that the DI, while not perfect in the AR platform, isn't necessarily  bad either. The piston system does account for some shortcomings,  but the "tube within a tube and off axis function forces" (piston rods offset from boreline) is the main weakness.

You clearly have no idea what you're talking about.

If there is any parroting of nonsense, this is it.

The amount of use and abuse .mil/.gov guns experience makes for a unique  crucible for weapons testing.

Even battlefield vegas doesn't compare. While they get high round counts and don't get me wrong, very useful information can be gained from their experiences, they simply don't see the actual use and abuse a system can experience in .mil/.gov hands.

I deal with.mil/.gov contract guns and equipment every day at work. This constant bullshit people spew about "lowest bidder" is what needs to stop.

It's amazing how quickly anonymous people on the internet will claim someone they have no clue about has "no idea" what their talking about.  You can have whatever opinion you want about .mil gear.  Having been involved in .mil contracting, bidding, and contract execution I will only say that they are the minimum, not the maximum.  .mil spec is the baseline.  There is much better out there.  The story of the Bradley Fighting Vehicle is a perfect example of how .mil contracting works and why it's not the gold standard.  .mil is the bare minimum.  That does not mean they are junk.  It just means they are the minimum for acceptable.  And I don't care one second what you think.

Ayup, you have zero idea what you're talking about.

Clue: equipment that meets the milspec standard does in fact meet the minimum standard.  What thT DOESN'T mean is that the standard is crap.

This most basic assumption on your part speaks volumes of your actual knowledge on the subject.

F15's, F6's, A10's, and nuclear submarines as well as their nuclear payloads also meet the "bare minimum" standard, just as the M4 does. Coincidentally,  so does every Rolex sold as does every doctor you visit, dentist you let work on your teeth, every car you drive, etc.

By your presumptions, every single piece of governemt equipment is utter shit.

Old joke: what do you call the guy that graduates at the bottom of his class in medical school?

Doctor.

Once again, i work with this gov. purchased equipment every day i work. I see reliability, durability, and quality. How well they handle abuse, maintain accuracy, etc.  I'm not a flappy head in a suit pencil whipping contracts who never usea or even sees the equipment in question.

Your premises are crap, suit boy.

Nice try bringing up the bradley. A weapons platform designed by a comittee of talking heads like yourself with zero operational experience, that in the end, the final product met every minimum standard those idiots set AND in the end, by pure accident, performed very well in two gulf wars.

P.S. if you didn't care what i thought, you wouldn't have replied.

I think you have reading comprehension issues.  Full disclosure, I didn't read this whole post.  Cause remember, I don't care what you say.  I will say that I never once said that mil spec is crap.  I just said mil spec isn't the gold standard.  Mil spec is acceptable.  Its the bottom line at which things could be considered usable.  There are a lot of manufacturers that are below mil spec.  Mil spec is like par in golf.  You did good.  There are many manufactures who exceed mil spec.  And exceeding mil spec is a good thing.

Well, I apologize on my leave of absence, life once again strikes and puts a damper on my plans. Unfortunately it looks like I missed some action that went down here in my humble thread, to which I'm too late to address the off topic shots being tossed around between fellow users, which is too bad because we're all brothers here gentleman, let's please try and always remember that.

As has been stated, I already have the kit, and I do completely understand that it's not an easy, simple task to switch methods of operation of a firearm with retrofit drop in parts, and that a firearm designed from the ground up to be piston driven has far better chances of operating without headaches.I will say this though, besides my having to modify the op-rod length, this kit was literally plug and play. Meaning yes, I have test-fired it, successfully I might add, after I rotated the gas plug 180° and turning the gas to FLOW, versus OFF, LoL, operator error is the #1 cause of firearm malfunctions(I made that up, it could be true, but I think it's magazine issues). Now, I have only run 2 20rd mags through it, as the range trip wasn't planned and I got stuck with not much time to do a lot of test firing various newly acquired firearms of which I had no clue whether they worked or not yet(because a firearm is the last thing you'll want to just assume works, I never will). Meaning, only time will tell how long the op-rod will hold, I'm thinking if getting some ½"x2ft cylinders of 4150 bar stock and having them turned to the dimensions I need, JUST IN CASE, but I wanted to ask the community if they could think of a more suitable material than 4150 to be used for an op-rod (please, I will unleash the plagues if someone suggests D2). It may be for nothing, as per Superlative Arms, there's supposed to be about the thickness of a piece of paper between the strike face on the BCG and the op-rod, and I think I'm sitting right in it nicely, so that's really my own cause of failure concern, IDK how it'll effect reliability, again, time will tell.

I again thank y'all for sharing your knowledge, as well as some opinions and beliefs, but because "mil-spec" had to be brought up, I get to chime in too. Mil-spec is a very broad term generally, so we'll refer to it as it applies to the AR-15/M4 platform. Mil-spec is, like mentioned, is basically a set of guidelines or minimum requirements something must meet in order to be considered fit for service, though it can also apply to methods of testing said something must undergo to be considered fit for service, example is the SP/HPT/MPI the bolts must undergo, along with the barrels I believe. The biggest caveat to the almighty mil-spec is ITS FREAKING OLD!!! Most major and critical mil-spec requirements are older than we are(obviously dependent on age), being they were established somewhere around the late 50's and mid 60's, and not much has been revised or updated since. The why is because why fix what isn't broken? But let's consider the technological advances we have gone through since that time, especially in materials science, so my stance is that mil-spec works, I can't argue that seriously with a straight face, BUT, one simply CAN NOT say that vast improvements couldn't be made if the mil-spec was brought up to date. The problem is the US gov't is the only one who'd air drop pallets of US currency on such a problem, outside of that, we have a good number, and growing number, of manufacturers that are starting to apply today's technology into our beloved AR pattern rifle, and I for one applaud and support them in the little ways I can. The issue is, and I hate to say it like this, are the "fudds" who think mil-spec is the end-all, be-all and will die on that hill, to them anything that's not aligned with mil-spec standards is basically blasphemy and should be burned at the stake for the witches(warlocks) that they see us as. I won't get into details here, I'm already in "rant nobody will read" territory, but I think the biggest issue is the lack of understanding as to what mil-spec is or refers to, but whatever, we all have Google and the vast wealth of information in our hands, so I just can't argue with folks that'll stand by that our 1960's technology is just as good as what we have available today, anyone with half a FUNCTIONAL brain should know that that simply isn't true. Ultimately would a 21st century built AR work any better or more reliable than our good 'ol mil-spec rifles? Well, of course they would, but not in major, obviously noticed ways that would justify the drastic price increase that would go with it. Things such as better accuracy that's repeatable for longer and while the barrel is hotter, lighter, shed heat faster, easier to clean, for longer wear cycles, if any at all(inconel, anyone), stronger and more robust, as well as more resistant to the elements. I could probably go on, but this is already too long and isn't gonna be read anyways, so, I'll keep y'all posted if anything happens/changes/catastrophically fails, LMK if anyone has any questions or inquiries they'd like to request of me, and I'll see if I can help in any way, thanks again everyone!!!

when properly installed, there should be roughly 0.016" free travel in the op-rod.  The installation instructions go over how to properly achieve that gap....basically install the op-rod, then install and fully tighten the op-rod plug, slide the gas block down to the shoulder on the barrel, insert the bolt carrier and push it all the way in against the op-rod until the carrier stops.  At this point, tighten the gas block screws.  Then, and only then, turn the gas port plug out ONLY until the flat screwdriver slot in the screwhead is vertical, with the long end of the slot pointing straight down at the barrel.  This will achieve that 0.016" free travel.