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Auto-chambering Repeater Concept Answered

I just got this idea a couple days ago talking to Jammy. Here's a crash course physics lesson:
When a larger object (a pin in this case) hits a smaller object (ammo in this case), only enough energy to make the ammo fly faster is transferred. This is because it takes less energy to make something of less mass move at the same speed as something with more mass. So as soon as enough energy is lost in the pin and gained in the ammo, they fall out of contact and the rest of the energy in the pin is wasted.
You can't really make pins any more efficient than they already are, so I figured I'd try utilizing the otherwise wasted energy. I figured one of the ways you could do this is by making a gun that automatically chambers a round after being fired. It'd be like a bolt action weapon except instead of manually operating a bolt handle, the extra energy would load the the round for you. The result is less effort and more efficient pin use. People may think this is less reliable than manually operating the bolt bin, but I beg to differ. This, in theory, would provide a more consistent chambering action. As long as it's fine tuned, the rounds should load exactly the same each shot. Also, you wouldn't be able to screw up chambering an extra round. You can pull the bolt handle back on a cocked bolt action weapon and easily jam the mechanism. With my concept, you can only chamber a round after the currently chambered one is fired (unless you purposely fiddle with the back of the gun) because the bolt pin relies on the firing pin to operate.

I have the front of this gun finished, but I still need to design the bolt pin assembly and the back of the gun to hold it so that I can actually fire this thing, but I'm confident it'll work out very well once I do. Here's a video to demonstrate the concept.

I'm hoping that once this gun is finished, it'll be a viable war weapon, seeing how I don't have anything better than my Oodassault at the moment. Or at least if I can't finish mine, someone else can use the concept.


I don't see how this can get a faster fire rate than something like a ZKAR, because you have to grab the pin, pull it back, let it go, pull the trigger, and then grab it again and repeat. With a dedicated handle, you always have your hand in the right position. I can fire ~2 shots/sec with a normal bolt action gun, but with something like a TR it's much slower. So while this is a cool concept, I don't see it actually improving anything.

But keeping your hand on a bolt handle is just begging for poor accuracy. Not only do you not have your hands placed for properly steadying the gun, but you're going to almost always take it off target while pulling the handle back. If you want a gun with a high RoF, a pump would be a little better. And, with training, you should in theory get a better RoF if you just got used to grabbing the pin and letting go as soon as it locks because then you're not wasting a motion setting the bolt handle back. Anywho, the other benefits of this concept still stand. If someone really wanted to waste the sections of pin adding a charging handle, it'd still be more reliable than a manual cambering weapon.

>implying that aiming a knex gun vs just pointing and shooting actually gives you an advantage.

I can do 2 shots/second with my ZKAR, and it is so light I can hold it at arms length and have it be still. I can't do anywhere close to that with a normal pin gun.

Love this concept.
I'm starting this tomorrow! Credit to you of course.

I believe it has great potential once it's perfected. From a user's view point, it is essentially just a regular mag fed gun that gets the range of a manual chambering weapon but you don't have to operate a bolt.

I'm reviving this thread to mention that I just came up with an idea to maybe make this concept work out better. It'd also allow a normal lengthed bullpup. If the pin went over the magazine a little so that the pin itself actually hit the exposed ammo, it'd "shoot" it into a separate chamber. This chamber would be like a mini lever action actuated by the trigger. When the trigger blocks the pin, it also raises the chamber to load a round. When the round is fired, it resets the chamber to immediately receive the next round. I don't exactly know how this trigger mechanism would work out yet, but the idea is to separate the loading and firing chambers so they never interfere like in my last design.

sounds like a fun concept! Gotta show it off when you can. Maybe at the war in 2 weeks???

Sorry, don't think I can make it. I'm working on my parents' house even after school starts, so I'll be busy moving my stuff into the apartment with my friends, cleaning up this house, and then preparing for school the entire weekend.

The only issue I can see would be the fired piece not having entirely left the chamber before the next one is pushed up, leading to a jam.

Already before discussed and why I didn't continue on this gun. I'm currently working on reworking the concept to get around that issue.

That's a fiddly problem to solve, good luck with it.

ok, so i made a nice gun with this concept, and i made a video of it, and it'll probably be up in an 'ible tomorrow, along with another new invention... you'll see. but i don't really know how to make mine more reliable (it's not perfect). and also, while reading down the comments of this topic just now, i see you said at the beginning that you would prefer for anyone working on this to do so with you in a collab, and i would like to try and give your version a shot, coz i imagine it's better than mine. so if you're still interested in this concept and haven't finished or collabed with someone else on it yet, i'd be glad to check it out.

Give it a shot. I'm more of a guy that likes credit for the concept and not the working weapon, even though I know it's building the concept that is more work. At the time I just wanted to make it work because I'd finally have a gun that could reasonably compete with our other war weapons, but I've given up for now. So if you can make it work, by all means, do what you must. I'd love to see a working version of this concept no matter how it is built.

i have it working, like i said, but i still want to give your's a shot because it looks like it's better. do you still have it? if so, a pic or two of the internals would help me a lot. thanks anyway. i'll give you credit on my 'ible

yes, but my time has freed up drastically due to no more tests for me this year, so i missed building and i'm back for now (i realize i wasn't away for too long in the first place). anyhow, do you want me gone?

No,no,no I didn't mean it like like I was just throw off by your name.

by the way, how were you gonna have the ram hit the bolt pin? and how were you gonna have the bolt pin pulled back while cocking?

As much as I like the compactness of mine, I don't think there'd be enough space between the currently loaded round firing and the next one loading.

I was gonna have a moving back "barrel" I guess in front of the trigger that connected to the bolt pin. So after already hitting the round, it'd hit the back and move the bolt pin. And then that part was simply gonna be rubber banded so that it wanted to stay back by default and would only be moved forward under the force of the pin.

The trouble with this concept is that it's a Goldilocks thing. You want enough room for the next round to load, but you also want a small distance between the back of the gun and the trigger for the bolt pin to travel, so you'd have to make it just right for there to be enough energy to transfer the next round into the barrel.

My solution is making a sliding barrel assembly, trigger and all, within the body of the gun but still independent of the magazine. So when the pin crashes into the back of the gun, the entire barrel and bolt pin would move forward so that you don't need to worry about the length needed. Of course this would be complicated in itself.

So yeah, how about you just focus on the one you've made just to get a working version of this concept out, and we can improve on it after we see it.

ok... what you're implying might be too complicated to make in any proportionate size, if possible at all. btw, mine should be up in a few minutes, so you can check it out.

This would be useful in bolt action pistols, because in a normal bolt action pistol you might pull the bolt right out of the gun.

The key to this gun is going to be the location of the loaded round. The energy transfer takes place in a fraction of a second, so if we can make the ram contact the bullet before the bolt, there should be little to no energy lost due to the bolt function. However if it comes into contact with the bolt prior to the round, it will be decelerating by the time it hits the round, resulting in a loss of force. So layout is key. I would work on it, but I am tied up in another project. I'll give it a go when I am done.

Don't worry, I already figured it out. Sure, the bolt would be hit after hitting the actual round, that was the point of this concept, but I was still worried that even with the pretty fast velocity the bullet would be going at, it still wouldn't be able to clear the entire distance before the ram would hit the bolt pin into the round up the ramp. So, yeah, that means I simply need to increase the distance the round has to travel before it is chambered. Well, my current design doesn't really allow for much room. If I move the barrel + trigger forward, I shouldn't have much problem. I figured if possible I'd try making it bullpup just because this system would allow for a shorter stock and it'd actually be more convenient for the handle to be out of the way of the bolt pin system. Otherwise I should be able to make it work for a traditional layout. I may or may not get to work on it tonight depending on whether I go out with friends or not.

I got you. I hope you can do something with this, it seems very promising. I am also going to play around with that other mechanism we were talking about in that other forum post. That one seems cool as well.

Well here I go reviving a topic for the sake of stating that I may or may not reattempt it. I have an idea on how to improve this concept. But I'll have to destroy my just-for-fun gun first, so once I'm finally bored of it, I'll attempt this. I'm not making any promises, though. But just in case any of you were wondering what I'm working on, here you go.

Hey do you have any better pictures of the gun? I think i might give this a go tomorrow im a bit lost on the second grey rod though and how that will move forward, could you try and explain it somewhat?


6 years ago

Hey TD, I think I have a solution although I'm not able to make the gun from that single picture and I can't try out the thing in my head.
I suck at describing things but I'll try.

In the 1st and 5th layer, at the very back of the gun, you have red 3 way connectors with a white rod. Connect to that white rod two orange connectors. On the other end of the orange connectors another white rod. Between it put a grey 1 way connector with a red rod that goes trough the gun.

When the gun shoots, it'll push the ammo out first, because a grey/black rod is longer, than the ram rad will hit the insides of the orange connectors which will push the red rod forward as a bolt, but than not attached to the ram rod.

Hope it's clear

I think it snugs perfectly. You have to remove the two yellow 5 way connectors though, but that isn't problem, I suppose?

This looks great TD. A step forward for compact powerful guns. I like how you make you guns as small as possible and use the least amount of pieces (I know you are limited) for them to function well.

A cross-sectional picture would be nice, if no instructions/pictures are put up, it looks simple to make.

Anyway good luck with it, and if it fails, show the community how to make it so someone will carry on with it or turn it into a bolt action if they can't.

Sadly, I destroyed it already because it would be easy for me to build again. I was tempted to just turn it into a bolt action seeing how I decided I'd need to redesign it for my concept, but I figured that'd be silly if I was gonna end up doing my concept anyways. But I don't know now, I lost the motivation to continue it and hope someone else will give it a go. I'm trying to think of a new way to revolutionize weapons via simple things.

Um is there something wrong with a rubber band loading it in? Or is it just for the heck of it?

Yes, directly feeding a magazine into a gun results in A LOT of friction which reduces the range of the gun quite a bit. Individually chambering the rounds separates the round from the friction of the magazine.

Yay. Good ideas make me happy.

Firstly, you are right about the pin's speed limiting the speed of the ammo. But ammo will actually shoot a lot faster than the pin. That is because the plastic flexes, increasing the impact time. It makes a huge difference.

Now about the efficiency of your design. Your idea requires that the ammo be hit before the pin finishes its travel. That's the only real downside I see. The range loss would be noticeable, and may make the idea not worthwhile. Especially because bolt action is to maximize efficiency.
On pin guns, the extra energy goes to the back of the barrel. So instead of interrupting the pin, try to make the back of the barrel move. It would mean that even the trigger block needs to move with it. It wouldn't be as reliable as your idea because my idea only uses the energy of the impact. If the impact isn't enough, the next round won't be chambered.

I suppose I didn't take into account the elasticity of the plastic pieces, though couldn't the same be said about the firing pin? Obviously there'd be less flexing in a black/clear rod, but there's also more length to do so. I can't image it'd be a huge difference, but I have no way to measure that personally. If someone could actually measure the speed of a firing pin and the speed of ammo being shot out, that'd be helpful.

I guess I didn't clarify enough that people would get this. I did intend to make the back of the gun move. I didn't really have a lot of space I realized with the trigger, but I was hoping that the initial shock, a "short stroke" esque action would "shoot" the round into the barrel instead of needing to push it all the way. I don't know for sure, I haven't finished the gun, but I think I might change it now that you suggest having the barrel move. You could remove the bolt pin entirely and just make an extension of the barrel push the round. And as long as you hook the bands up right, it should always reliably feed because the bands would continue to pull the barrel against the magazine until you cock the pin.

Alright, I'll begin planning out an updated version of the concept using a sliding barrel.

I think I understand. This prevents chambering of multiple rounds, right?

Well, it's just a bonus I noticed on the fact that the gun is rechambered by the firing pin, and thus the previous round will have to have been fired. The only way you could mess it up is if you purposely tried to, like to slowly decock the pin with a chambered round, or to push on bolt pin yourself.

Alright. It sounds efficient and simple to do. I'm surprised it hasn't been done.

Great idea! I can see this being a very reliable mechanism and with it you will be able to make more realistic looking guns

i see where your necessity to utilize the wasted energy comes from, but this isn't a very good way. i don't actually know how you could utilize it better, but i can try to think about it. this is unnecessary because you have to cock the pin anyway, meaning pulling back the bolt, so what difference does it make for the user? also, this concept is fairly simple to build. what are you talking about with how hard it is and how you need a collaborator? also, in this potential concept, once the pin would hit the auto-bolt, it would loose some of it's energy, thus creating a situation where the gun would be weaker, because less energy would have been transferred to the ammo. also, there would still be the same amount of potentially wasted energy. nice try though. 4*

*sigh* I dislike needing to repeat myself.
1. You have to cock the pin and only cock the pin, you don't have to fiddle with a bolt handle which take up pieces, usually a lot of pin space, and can interfere with band placement. That in itself is a "why not?" motivation behind this concept.
2. Also, consequentially, this concept is in theory more reliable due to consistency than a manual bolt action would be.
3. This concept is rather simple in essence, surprisingly enough it has yet to be done, though. I don't have the pieces to finish the stock. So if someone wanted to build off this they could.
4. You don't get the point of this demonstration. I said I didn't finish the back of the gun. The idea is that the pin will have already hit the ammo before hitting the back of the gun which then would be connected to the bolt pin. I was just using a grey rod for the demonstration to load the round.

First off, don't patronize me !
1. Why not is ok, i was just stating that i don't see how it would help...
2. Agree to disagree ?
3. I get the missing pieces part, but the reason nobodys done it is that most people don't try to think how to be innovative, they just remake all the existing mechanisms into a gun
4. You didn't state that... How could i have known?...

Anyway, look man, i'm not trying to be mean or anything. I was merely expressing my opinion and leaving some constructive criticism with it. Don't take this the wrong way. I'm sorry if i offended you man.

1. And so I explained how it would help. It doesn't hurt, it may not make a huge difference, but there are little gains.
2. Fine, not bothering, but I'll just say I dislike how everyone has been brainwashed to be distrustful with anything that has a rubber band attached to it.
3. Well, nothing's left to discuss here then. Sure, it's simple, but no one else did it yet, so I did, but I don't have the pieces to complete it, so I'd like to see if someone else would want to. That's all.
4. I'll admit I did not explicitly state in the thread that the concept worked that way, but it was greatly implied after stating the whole wasted energy thing and then the chambering a round with this wasted energy. And then in the video I made it perfectly clear.

I don't find offense in criticism unless it is false. I only counter criticized your reading comprehension because you criticized the concept without actually knowing exactly how it worked. But no matter, I'm not trying to argue. Now you know.