6mm Semi-auto : Fully working blow-forward, 150 RPM + Vids
Posted: Fri Jul 18, 2008 5:57 pm
6mm Semi-auto : Fully working blow-forward bolt, Approx 180 RPM
I proudly present you the working version of the project i have been working on for quite a while, please bare with the poor aestetics, this is the beta version of a desing that i plan to incorporate in a more convenient form :
First of all i'd like to thank JSR for sharing his work on the blow-forward bolt/piston on this forum, his work obviously inspired most this launcher.
Here is a quick diagram of the inner parts of the gun :
As many will notice, there is nothing realy new in this desing, at first it may look very simple, but the version of the launcher is actually the fourth try at getting a reliable, quick and stable semi-auto mecanism. My main problem in the construction of the launcher was :
- The only epoxy availble in Canada is epoxy putty, so all casting using epoxy is very hard or simply impossible for me.
- I have access to no specific tools exept a drill.
One may say that i could have simply bough the missing tools and ordered some low-viscosity epoxy, but i actually wanted a mecanism that was simple to make and did not required any special machining. The first desing i wanted to make was this one :
It is exacly JSR's semi-auto on this page :
http://www.spudfiles.com/forums/6mm-sem ... 10075.html
My version of it unfortunatly never worked properly, i had exacly the same problem that JSR had when he made the original device. The rate of fire was terrible because the bolt would take an awful lot of time to reset back in it's first position. The reason why was that the piston was heavy to move and could not gather any momentum, so the air simply leaked slowly into the bolt. To solve this problem, i needed a desing that would allow air to be contained in a "secondary" chamber so that the bolt reset's automaticaly. Hence the setup that was used on the present launcher :
When the bolt move forward, it as enough momentum so that almost all air dump into the secondary chamber. From there, the air can go trough the bolt and push the projectile. Unfortunatly, this design cut the pressure in half, resulting in relatively weak power overall. But when i built it, i was looking for ROF, not power, and i feel i kinda reached my goal.
Here's a quick video of the launcher bolt movement and the launcher shooting at different speed.
EDIT :
Even though this is a working device, it as the disadvantages of not being able to go full auto under a constant flow of air and a noticeable lack of power. I do not think that the blow-forward bolt is the solution to reach full auto, the problem being manly the spring, wich need to be choosen carefully so that it's strengh allow for a reciprocation of the bolt/piston.
I had an idea of a springless bolt, based on the inline valve, wich i will open a thread about it later.
I would very much like to hear what the members think about this, i will be glad to accept every single comment, would it be good or bad. Thanks for reading!
I proudly present you the working version of the project i have been working on for quite a while, please bare with the poor aestetics, this is the beta version of a desing that i plan to incorporate in a more convenient form :
First of all i'd like to thank JSR for sharing his work on the blow-forward bolt/piston on this forum, his work obviously inspired most this launcher.
Here is a quick diagram of the inner parts of the gun :
As many will notice, there is nothing realy new in this desing, at first it may look very simple, but the version of the launcher is actually the fourth try at getting a reliable, quick and stable semi-auto mecanism. My main problem in the construction of the launcher was :
- The only epoxy availble in Canada is epoxy putty, so all casting using epoxy is very hard or simply impossible for me.
- I have access to no specific tools exept a drill.
One may say that i could have simply bough the missing tools and ordered some low-viscosity epoxy, but i actually wanted a mecanism that was simple to make and did not required any special machining. The first desing i wanted to make was this one :
It is exacly JSR's semi-auto on this page :
http://www.spudfiles.com/forums/6mm-sem ... 10075.html
My version of it unfortunatly never worked properly, i had exacly the same problem that JSR had when he made the original device. The rate of fire was terrible because the bolt would take an awful lot of time to reset back in it's first position. The reason why was that the piston was heavy to move and could not gather any momentum, so the air simply leaked slowly into the bolt. To solve this problem, i needed a desing that would allow air to be contained in a "secondary" chamber so that the bolt reset's automaticaly. Hence the setup that was used on the present launcher :
When the bolt move forward, it as enough momentum so that almost all air dump into the secondary chamber. From there, the air can go trough the bolt and push the projectile. Unfortunatly, this design cut the pressure in half, resulting in relatively weak power overall. But when i built it, i was looking for ROF, not power, and i feel i kinda reached my goal.
Here's a quick video of the launcher bolt movement and the launcher shooting at different speed.
EDIT :
Even though this is a working device, it as the disadvantages of not being able to go full auto under a constant flow of air and a noticeable lack of power. I do not think that the blow-forward bolt is the solution to reach full auto, the problem being manly the spring, wich need to be choosen carefully so that it's strengh allow for a reciprocation of the bolt/piston.
I had an idea of a springless bolt, based on the inline valve, wich i will open a thread about it later.
I would very much like to hear what the members think about this, i will be glad to accept every single comment, would it be good or bad. Thanks for reading!
