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
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whoops, bit of a double feed there, but given the overall ghettoness I'll let that one slip
Following on from my design concept, here's the finished product in action:
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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.
