Posted: 08/19/2007 1:15 AM Post subject: 6mm semi - added trigger & mag!
aspiring machinist
Joined: 15 Mar 2007 Posts: 18060 32518.54 Spud Bux
Update 08/20/2007:
I added a blowgun as a trigger, and the performance jump was impressive - velocity with 0.25 gram BBs averaged at 415 feet per second, more than double the initial velocity figures, and muzzle energy has gone up from 0.25 ft/lbs to almost 1.50 ft/lbs, that's a massive 6 times increase! You can tell the reason for this increase by comparing with the first video, thanks to the higher flow of the blowgun the bolt actuates visibly faster. Now the blowgun has a particularly sh!te flow, so I know it can be even better
Now that it had a trigger, I just *had* to make a ghetto mag and video it, enjoy
As you can see, the original design goal of achieving full-auto fire with a constant flow of air has not been achieved, the the above video I am opening and closing the flow of air from the compressor manually. There is too much friction in the system (as one can tell by the low speed with which the bolt is re-set) and using my current construction methods - without the benefit of a lathe or a drill-press - I doubt I can get it any better.
Performance is a little on the disappointing side, I chronoed a 5 shot string at 110 psi using 0.25 gram BBs and got the following results: 172 fps, 158 fps, 161fps, 149 fps, 157 fps. This could be improved by increasing the flow from the compressor and adding a "buffer" chamber to the rear of the bolt.
For completeness sake, here's the internal concept diagram:
bolt during construction:
completed breech:
I could easily use this to make a semi-automatic pellet gun, or pulse the air for full auto, but what I really want is full auto operation with constant airflow so I'm shelving this idea for now.
For more detailed information on using epoxy, check out the how-tos here and here.
Last edited by jackssmirkingrevenge on 09/10/2007 11:16 AM; edited 4 times in total
Joined: 15 Mar 2007 Posts: 18060 32518.54 Spud Bux
Actually I'm diappointed, I was really hoping for full auto. No leaks are apparent, though i'm sure a little bit of air leaks between the bolt and the barrel on firing as there are no o-ring seals.
Performance is approximately 0.25 ft/lbs, which is fairly decent by airsoft standards but I was hoping for something a little better. Ah well, back to the drawing board.
Concidering that, that is the 1st fully working model, I'd say you have done really well. Least you know the concept works well and you know things can be done to improve it.
Joined: 15 Mar 2007 Posts: 18060 32518.54 Spud Bux
I cut a vent in the forward portion of the body tube, average velocity went up by around 50 feet per second as the bolt is now encountering less resistance and opens quicker.
Still, this looks to be a bit of a dead end for my auto dreams.
Whoa, how did I miss the concept thread? THis looks terrific. Sorry the auto didn't work out for you. But I think you are on to something: that would make a nice semi-auto for sure.
Btw, have you looked at my [url="automatic hammer"]http://www.spudfiles.com/forums/the-auto-hammer-t9935.html[/ur l] design? There's some similarities to this gun; perhaps you could cross the ideas and get somehting better.
Edit: blast, can someone tell me how to fix that link business?
I had seen you design, while in theory it would work it seemed a little too complicated for my liking. I'm now inclined to try making this design, it would be much simpler and quicker, plus easier to adjust.
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