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6mm semi - added trigger & mag!

Built a BB Machine Gun? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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6mm semi - added trigger & mag!

Unread postAuthor: jackssmirkingrevenge » Sun Aug 19, 2007 2:15 am

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 :D

Now that it had a trigger, I just *had* to make a ghetto mag and video it, enjoy :D

[youtube]http://www.youtube.com/watch?v=LfHw-DCoCDs[/youtube]

[youtube]http://www.youtube.com/watch?v=BmPjKk9neVM[/youtube]

whoops, bit of a double feed there, but given the overall ghettoness I'll let that one slip :D



Following on from my design concept, here's the finished product in action:

[youtube]http://youtube.com/watch?v=F1_dbDbuHHo[/youtube]

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:

Image

bolt during construction:

Image

completed breech:

Image

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.
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Last edited by jackssmirkingrevenge on Mon Sep 10, 2007 12:16 pm, edited 4 times in total.
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Unread postAuthor: Mitchza89 » Sun Aug 19, 2007 2:22 am

Wow... Thats unreal mate. I really take my hat off to ya for this one. Huge job well done.

Does everything seal alright? Good performance?
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Unread postAuthor: jackssmirkingrevenge » Sun Aug 19, 2007 2:32 am

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.
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Unread postAuthor: Mitchza89 » Sun Aug 19, 2007 2:34 am

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.
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Unread postAuthor: jackssmirkingrevenge » Sun Aug 19, 2007 4:22 am

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.
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Unread postAuthor: Redcoat » Sun Aug 19, 2007 4:32 am

It's a nice gun and i like i.To be put into Auto would be awesome :shock:
BTW, where do you get syringes from?

Happy Spuddin'
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Unread postAuthor: jackssmirkingrevenge » Sun Aug 19, 2007 4:48 am

Redcoat wrote:BTW, where do you get syringes from?


I either steal...er... "borrow" them from work or buy them from a pharmacy ;)
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Unread postAuthor: Redcoat » Sun Aug 19, 2007 4:49 am

a pharmacy eh? *tip toes out quietly in balaclava*.
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Unread postAuthor: experament-u2 » Sun Aug 19, 2007 4:54 am

even though you see it as a bit of a failure jack, i think its simply awesome, great work (as always)

would it work better (faster) if you could find a way to vent the air out of the area behind the bolt as its moving back? just a suggestion

oh and its being bugging me but whats that black disk between the bolt and the barrel, the one were the spring passes through?

anyway good luck on your quest for auto fire
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Unread postAuthor: jackssmirkingrevenge » Sun Aug 19, 2007 4:59 am

would it work better (faster) if you could find a way to vent the air out of the area behind the bolt as its moving back? just a suggestion

oh and its being bugging me but whats that black disk between the bolt and the barrel, the one were the spring passes through?


It's not the air that slows it down but the friction between the piston and the syringe tube, it's a very tight fit.

That black disk is a ring of moly grease I used to lubricate the tube, it collected at that point because that's the end of the bolt's travel.
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Last edited by jackssmirkingrevenge on Sun Aug 19, 2007 5:16 am, edited 1 time in total.
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Unread postAuthor: rhys_pesantsrevolt » Sun Aug 19, 2007 5:09 am

make a automatic
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Unread postAuthor: jackssmirkingrevenge » Sun Aug 19, 2007 6:38 am

oh alright then :roll:
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Unread postAuthor: Skywalker » Sun Aug 19, 2007 7:17 am

Whoa, how did I miss the concept thread? :shock: 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[/url] 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?
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Unread postAuthor: jackssmirkingrevenge » Sun Aug 19, 2007 7:28 am

(url=http://www.spudfiles.com/forums/the-auto-hammer-t9935.html)automatic hammer(/url)

Replace the round brackets with square ones ;)

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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Unread postAuthor: mopherman » Sun Aug 19, 2007 8:44 am

this looks amazing jack, you seem to be the only one here to be trying anything new.
were de you work, if you dont mind me asking?
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