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Well, initially intended for fully automatic cycling, this compact little 6mm multi-shot turned into an over-engineered hammer valve after my lack of a lathe made a low friction sealing face nigh on impossible.
Instead of scrapping the gun after initial tests were less than successful, I decided to transform it into a 6mm bolt action, fully capable of being magazine fed, but piss poor performance when it's correctly configured for mag feed (again, god damn those seals) So instead, at the moment it is muzzle fed.
The feed system was based on a fully automatic version of the Girandoni, that I designed and tested to great success at an earlier date in a testing rig, sadly the success was a one off, and this little beast will never hear the magical 'dakadakadaka' that it was intended for.
The two inline valves are both cut-down schraders, delivering enough gas for around 100 power shots (high-end airsoft power) all on a single fill, and the trigger is fully customized to have the 'perfect' weight when firing.
All the parts were made entirely by me, no lathe, no milling machine, just one determined guy and a file set, and all parts were soldered together, and hydro tested to 300 psi, no leaks.
I have a few pictures of when I was making it, and very few of it completed, I *might* put some firing and/or damage shots, but it's nothing worth shouting about.
If your interested in trying to make it work yourself, or alternately just want to have a clean looking compact hammer valve gun I have a full set of machine plans that I made, be good to see someone other than myself to put them to good use.
Please ignore the awful editing of the video, I really couldn't be bothered to rotate all the pictures, and chronologically it makes very little sense. It was done mainly because all the pictures were over the s'files 1mb limit and this seemed the easiest way of overcoming that, but, all the same, here it is:
As always any questions, asks, or criticisms are always welcome, I know I haven't explained nearly half of what need be, so don't be shy in asking,
The fully automatic dakadakdaka in the video* was achieved by partially blocking of the breech so that the gas could only escape round the bolt, which really shows how much of a bad fit it was!
Video of it cycling and pictures
*(please ignore my bad tastes in music in the background...
Last edited by jrrdw on Thu Oct 17, 2013 2:51 pm, edited 2 times in total.
Reason: Fixed video's.
Great job, just think what you could do with some machine tools! Think about investing in some
Do we get to see it in action?
Thanks And yes, in fact it makes you truly appreciate what you could do with machine tools when you have to try so hard to avoid designing things that would require them.
You can do some great things with store bought parts and some ingenuity, but epoxy and schrader valves will only ever let you get so far. Recently, after I finished this I did a bit of searching around and found a bloke who will let me use the 5000 pound lathe and 20,000 milling machine he has, so you might start to see some more from me in the future...
Action shots? Of course! Just waiting for the near eternal English rain to start clearing from the skies
Excellent, great way to get started
So I guess we're never going to see it work then
Last edited by jrrdw on Thu Oct 17, 2013 2:44 pm, edited 1 time in total.
Reason: Fixed video.
Edited for video and pictures*
Been bad weather for quite a few weekends now so I gave up and did some videos inside instead!
If anyone is wondering about power, even though the bolt leaks gas around it like a sieve when it's fired, it can still punch a 6mm 0.2g bb through 4mm corrugated card, so it's not bad for reaching on 100 shots per fill.
I'm not sure how it works, but my best guess the barrel is connected to the hammer, breech "seal" while the hammer hits the valves and opens for next round when it's recocked?
I have done similar thing in the past, the real tricky parts it's actually find a spring that has the same property of the rubber band (BTW JSR don't link me to ebay, I bought a good couple hundred and never found one)
Welcome to the angry wasp club
Pretty much my story with this one: spud-cannon-related/topic21364.html
Gas rams might be your best bet.
Re: 6mm Compact Copper Air Gun
why did you put the air tank on top,
how did you put the youtube videos on here....
Use the Youtube button in the full editor and paste/insert the direct link (from the 'share' below the video) in between the center brackets ( [youtube]I[/youtube] ), where the red "i" is.
When life gives you lemons...throw them back they suck!
Thanks, and yes you're right...mostly, the entire barrel assembly is fixed in a stationary position, with the rear of the barrel being blocked off, the bolt is forced to move forward like a blow forward bolt once it hits the valves until it clears the blocked portion, moving far enough to block off the magazine and simultaniuosly load the next pellet,
The two places I can't get the darn thing to seal is around the sides of the bolt, and the inside of the bolt where it slides along the barrel, without the use of a lathe it was nigh on impossible to get a good tight fit or put some o ring grooves into it to actually make it function as it should, so in the video, I removed the barrel assembly blocked off the central hole through the bolt (the 'breech') and let 'er rip
Great! Do I now get a personalized club members t-shirt?
Well it didn't turn out quite how I wanted it to, but I was going for the whole mp5 look:
No, but you do get to make a lovely mother's day present
Are you sure?
O-rings do offer seal, but in exchange you get friction. Higher the pressure, greater the friction. I used to blaming lack of tools, but now that I have them, certain things do not get easier necessarily. GBB airsoft guns don't have airtight seal but they do work flawlessly. If I were you I'd search for tubes that fits well one around each other and use some lub with some viscosity for a good seal. After all you only need a fraction of a second to cycle the action.
Good points, I did try and use a tight fitting bolt, the one that is in action at the moment has less than a 0.3 gap between it and the sides of the copper pipe it's mounted in. After that, I found that changing diameter by adding PTFE tape simply makes it too hard to move and definitely not hard enough to hit the valves, even with a good bit of grease.
Ideally I could have got some k+s tubing with pretty much matching inner and outer diameters but they didn't sell it in the sizes I needed,
Paintball guns, with ideally designed o-rings of around 10-15% compression, have brilliant sealing characteristics with very low friction, and relatively fast travelling bolts.
What I've found out is at higher pressures the proportional increase of the force on a bolt far exceeds the extra friction that it would provide, proportional to the size of the o ring, with smaller o-rings getting a smaller reaction force from the walls of the tube and therefore a smaller coefficient of friction.
I think the reason GBB guns work relatively well is they employ a valve with a very good flow, opened very fast, releasing a vast quantity of mid pressure gas, making any gas lost a very small proportion of the total gas in the system and so consequently performance does not suffer.
Anyway, after my trials with getting this system to work I have managed to get access to some machine equipment, of which I am using for my next design (with some glorious glorious o-rings) at the moment it's just a few components lying around, but soon....
Not something fancy, but in the end I did got what I wanted.
The first set up failed beyond my imagination, even though the o-ring has really low friction(blow it with your lungs it will move) and 100% seal.
Thin o-rings has lower friction but wear off quite quick.
I was watching that topic, in fact, it was after seeing what you managed to do with your lathe that I decided that in order to create something semi=professional looking I needed access to one!
Well I shall go ahead with the design as it is, (might put the 'new' design up here in a few days) and if it turns out as anything commendable I will show thee world, but I'm not expecting much given that it will be the first thing I have ever tried machining...
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