No, the two mechanisms are actually very different. The reason it uses a string is because the point of the pivoting bow was to allow the tension to be concentrated in the pivoting sections, not in the area where the string contacts the bullet. In otherwords, when you pull back the string, you can then mkve the string around or do whatever because it is not taught, as a rubberband would be if you were using an ordinary bow system. However, a trigger mechanism for this type of setup is goong to be gery difficult to develop because the torque exerted on the small space that the trigger contacts the pivoting arms is enormous, and thus friction makes for a very hard trigger pull.

But dude, I think you should have continued on that project, it would have been amazing. You said the band got twisted up, right. Were you only using one string to pull it back? If you used two strings, each connected to the band with about a rod's width between them, it would likely get rid of any twisting motion. That would have really reinvented long range. If you don't go back on that project, I might just have to. I'll give you credit of course.

There is another concept I had a while back, I'll see if I can dig out the computer-sketch I made...

But anyways:
The reason that full and semi-autos are so difficult to make out of K'nex is because, unlike real bullets, each individual round does not come pre-loaded with a source of energy that can b\easily be released by a smaller source of energy. This could be achieved in K'ned by making pre-loaded "shells" for each individual round that would resemble cocked block-trigger guns, just without the handle and as simple as possible. These could then be stacked and, using the mag pusher as the ignition energy source, they would be pushed up continuously or semi-automatically so that the blocks release the pin and fire the bullet.

However, this poses multiple problems in the areas of bullet portability and in the loading process, as each shell will likely be awkwardly shaped. My idea is to create a cylinder that is fixed to the gun, and houses these pre-loaded pins, but not the bullets. The bullets would be housed in a vertical removable magazine that would line up with the cylinder, so that as the cylinder rotates, either by trigger pull (we could do 3 round bursts with one pull), or by a wound rubberband, the blocks in the cylinder releases the pin just as it is lined up with the bullet, firing it, and then the next bullet would pop up just as the next pin lines up and goes off.

Unfortunately I couldn't find the sketch I made, but I think you can picture it in your head. It will definitely be easier said than done, but if it can be done, I feel it will be one of the best guns ever made.

Great man, I'll start working on it too as soon as I can.

Well, because of all that's been going on lately I have been pretty dry on Ideas lately, which is why I am so glad that TD and Oblivitus are giving us some with their new series of challenges. I suggest you look into it as well.

But, I have gotten my new rail guided pump as good as I think it will get, and I could send you some detailed pics if you want to use it in something. It isn't too incredible in itself, but what makes it good is that it is a very useful supplemental concept, as it doesn't take up space that other mechanisms could occupy. I think it could be very useful in a sling repeater or rail system repeater. I will work on that sometime soon, but I am tied up with the "slingshotgun" that TD and Oblivitus came up with. If you want to try that idea that would be great.

A little over a week ago, TD posted The K'nex Innovators' Challenge on the forums.  It will consist of a series of challenges in which TD and Oblivitus provide a concept and the contestants are to bring it to life to the best of their ability.  Each challenge will last one week (with the exception of the first challenge), and the judges (I assume they are just TD and Oblivitus) will score each creation.  The "slingshotgun" was the first concept that they provided, and can be seen on the forum topic.

I have made a few slight improvements not seen in this forum, so if you want, I can post pictures.  As for the closed barrel sling, I get what you mean, but won't be able to provide any solutions (except add more glue!!!) without a better look at the internal layout.  But, there is a mechanism I made a few months ago that can actually "charge" a wound rubberband, or in this case, a string attached to a rubber band, bu moving a lever back and forth like in a lever-action rifle.  I can show you that one if you want, seeing that it is just lying on my bedroom floor.

Lol TD with the save!

That is actually pretty interesting. I remember thinking of a mechanism that would actually allow you to push the pump instead of pull, and it worked out in my head and everything, but then I found your contest haha. Maybe I'll remember what it was after I unveil my take on the "slingshotgun".

No, I don't think so. If you mean extended barrel when you say "extended ram concept", that basically means any type of rail system. As far as I am aware, every part of this gun is completely original. Everything in this gun worked as I had designed it to, but unfortunately the effort required to actually load the bullet is greater than that required to bull back the arms. Therefore it unfortunately cannot hold a large amount of bands and thus is pretty weak. I am currently working on something similar, but will resemble a shotgun more than a bow.

Ahh I remember that gun! I actually recreated it a while back. But yeah, he is using a rail system, just as I am here.

Thanks man. Well, I'm sure your bolt action works better than this one, because I am kind of stuck at the moment. Pretty much everything works, but the problem I am finding is that when you pull the slide all the way back, it is very hard to load the bullet with the extra tension of the bow on it. This may call for some major re-designing but I am hesitant to take it apart unless I am sure it won't work how it is.

I'd say I've put about 12 hours into it. It has been on and off because graduation is coming up and I have so much to do.

It consists of two sets of arms: a fixed set and a pivoting set. The pivoting arm is connected by rubber bands to the fixed arm, causing it to snap towards the fixed arm when pulled back and released. There will be a string running through the barrel connecting the two pivoting arms, so that when they snap into place, the string will drive the ram forward, along with the round. Imagine holding a string by both ends, but not very tightly so that the center droops. When you pull the string, the center snaps up. Same concept. Because the mechanism is not dependent on the release of a rubber band at the back of the gun, but rather two arms that are located at the front of the gun, the trigger can be located at the front, since that is where all the action is happening. I'll post a video tomorrow with my designs so you can get a better picture.

Kind of, except that the fixed are and the pivoting arm are not connected. The video will be up shortly and it gives a more visible explanation.

At the moment, it uses less, but the bow may change that.

I sure hope I don't, each of these mechanisms were designed to work together so if one doesn't work, then the rest are obsolete. But even if this gun does fail, I have learned more than I had ever hoped to through its construction.

Thanks!