Advantages of this concept:
Wow,you keep trying to reinvent the wheel.You should just get an AR and enjoy it! 
So the only real advantage is the ability to have a folding stock while in return adding more parts that can fail?
Or am I missing something? I understand how it works, very simple but I’m not sure what it brings to the table.
By “same level of complexity as the standard AR gas piston system” are you referring to the direct impingement system or the gas piston system? Because if it’s the former you are replacing the gas tube and roll pin of the DI system with multiple parts and springs. Not exactly simpler!
Also, is the gas key attached to the oprod in some solid way where the two will reciprocate together ala long-stroke piston? Because eliminating the receiver extension to allow for a folding stock will require the back half of the BCG to be cut off so it can reciprocate inside the upper, therefore the recoil springs will have to be up front to pull the bolt forward. I’m just saying this because the area in your diagram where it says “carrier key cup” makes it look like this is supposed to be some kind of drop-in that will work with the standard BCG which it most certainly will not. If it works at all.
It wasn’t interesting that HK designed a piston driven AR, it was interesting that they delivered working models to the user groups that needed them.
Understand?
Sorry, I don’t understand. Would you please explain?
I meant "The same level of complexity as the standard piston systems.
You are correct that the BCG may need to ‘saw’ away the last half. I did say minimum modification.
Basically this is the same design as the standard piston, except I rearrange the buffer tubes at the front.
Are you an engineer?
No. I thought the stone-age diagrams should be obvious enough about that.
I know you are trying but do you think this is a marketable item? Who’s going to see a perceived need to buy this? The AR-15 has reached a new era of maturity and direct impingement will always reign supreme, from Olympic Arms to Noveske and everything in between. Why not focus your efforts elsewhere where it might be more beneficial? Like another poster said, why are you trying to reinvent the wheel?
How exactly could you have a folding stock? When the BCG is fully inserted it is flush with the rear of the upper receiver. When it cycles, it has to physically move backward (IE: Into the buffer tube).
So, unless you have some truncated carrier design ala’ ZM/Para or Oly, a folding stock isn’t happening.
It is a draft concept/idea, nothing more.
I am afraid some level of modification is still needed. A gunsmith would have to saw away the last part of the BCG.
Why do we need an AR with a side folding stock arrangement?
We have been deploying the AR15/M16 for what 40 years give or take and collapsible stock variants for close to that. During that time they have been successfully deployed from vehicles, helicopters, fixed wing aircraft (airborne), armored vehicles, etc all without a side folding stock.
If you want to refine/improve this system (which is already pretty damn refined) you need to identify a mission critical need and then work on a solution to that. Something that decreases weight, improves accuracy, enhances capacity, lethality, or reliability, etc.
“Necessity is the mother of invention” right? A side folding stock is not a necessity. A desire for some maybe, a necessity no (obviously as this weapon system has been successfully fielded in just about every continent and environment in the world without one).
What Failure2Stop is saying is that H&K provided a working sample (actually several) for military testing and subsequent adoption, not freehand conceptual drawings.
If you are serious about your pursuits (which I’m not too sure about) I would suggest you keep your ideas, and drawings/designs to yourself as these would potential be lucrative intellectual proprietary and subject to theft. Build a working prototype. Test the hell out of it. Refine it, and repeat the process until you have a reliable, durable, and economically feasible product. Then contact a patent attorney and have them research your product. If everything is good to go apply for a patent and then either begin production or pursue selling the rights to your product to an existing manufacturer.
Good luck. I admire your desire and drive, but suggest you spend more time shooting the current system to determine what may need to be addressed, listening and reading, talking to end users, etc. Good products are rarely designed on a cocktail napkin overnight.
Just buy a kel~tec PLR16, slap a folder on it and be done with it.
Thanks for your advice. I absolutely love AR but I could not afford one (plus a place to store, accessories and utilities…etc). So… I entertain myself with my imagination.
Unacceptable. A new carrier would need to be provided. Go sawing half the carrier away and you are removing a significant portion of the reciprocating mass altering dwell time, the feed cycle, etc. You are also removing the buffer itself, or do you have it in your design (I don’t see it labeled). I fit is absent you are even further reducing the reciprocating mass. Unless you have taken this into account with spring rates, gas port sizes, etc. Change the gas port though and it’s not “drop in”.
Also dual buffer tubes requires, dual springs, buffers, etc increasing the parts count and complexity of the system.
I also just noticed the carrier key “cup”. Why wouldn’t the operating rod fit directly into the carrier key (because it has buffer tubes on either side below it)? Your drawing shows the op rod some distance above the carrier key. Also your barrel is not centered in the delta ring, more like in the lower 1/3. New Delta Ring assembly, new upper receiver. This additional height may also interfere with the receiver accessory rail height requiring new sights of a different height, etc.
Not “drop in”.
How do you attach the buffer tubes? To the barrel? To the gas/piston system? Put all the new weight from buffer tubes, springs, buffers (which need to be heavy to make up for lost mass in the system) and you’ve thrown a lot of weight on the front of the rifle effecting the balance. Attach this weight to the barrel and you are effecting barrel harmonics and accuracy.
Draw/post less, research, test, build, etc more.
Again I appreciate your desire and drive, I’m not trying to piss in your corn flakes. Learn and keep moving, refine, evolve. You’ll find lots of ways NOT to do something before you discover a good way TO do it.
Ok ok… I believe other off-the-shell piston upgrade kits also come with their own BCG… (Adam Arms come to mind).
So if a custom BCG would be provided, then this concept could be considered a drop-in kit, right?
The purpose of the carrier key cup is to secure the carrier key in place so that the rod could push/pull the BCG.
Aren’t you in Canada?
Yes. They are relatively expensive in Canada.
What is expensive for you? 1500$ buys you a high quality AR here, and you can get a 600$ Norinco M4 if you don’t care about quality.
How old are you? Do you even have a Firearms Licence?