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M4 m203

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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M4 m203

Unread postAuthor: koolaidman » Sun Apr 13, 2008 9:43 pm

Hey, ive made plenty of pneumatics before, but ive never made a bbmg. I have decided to build one for a friend. I was partly inspired by Singularity's clip fed prototype. This will work basically in the same manner as his, except more erognomic, more efficent, and it will have an "m203."
Basically the pictures say all. It's mostly pvc- but only the clip is pressurized. The stock is 1", the trigger is just 1.5" wye with a blowgun inside. The clip is the trickiest part. The tee is reducing 1.5"x1.5"x1", inside that i will glue a .75" threaded cap (they fit perfectly.) Ill epoxy the two airlines through the cap. This allows me to screw on the clip. This all cuts down on deadspace and means only the clip is pressurized.
The m203 is gonna be my favorite part. It wont exactly be the most powerful of pistons, but its only gonna shoot ping pong balls. Its a simple coaxial with a 2" chamber and a 1.5" barrel (only a 1:5 chamber-barrel ratio.) The piston will be a 1.25" endcaps with a neoprene washer piloted by a .25" ball valve.
If it all works out well ill add all the finishing touches. The sights, the sight on the end of the barrel that flips and compensates for range, paint it black, and maybe even a small ball valve for a safety.
Im posting this so that i get some feedback and criticism before i build. The one challenge that is apperent by the diagrams is my lack of knowledge for compressor and airline fittings.
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Unread postAuthor: blind909 » Sun Apr 13, 2008 10:21 pm

you will have to turn the blowgun around, or it will leak, you have to have the 1/4 inch npt threads connecter to your compressor.
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Unread postAuthor: jrrdw » Mon Apr 14, 2008 7:28 am

Looks good in design. Once you start putting hands on the air line fittings will be no problem for you to get the hang of.
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Re: M4 m203

Unread postAuthor: judgment_arms » Mon Apr 14, 2008 8:59 am

koolaidman wrote:...Its a simple coaxial with a 2" chamber and a 1.5" barrel ...

You may want to use a smaller barrel: 2in SCH40 PVC has an ID of ~2.049, and 1.5in SCH40 PVC has an OD of ~1.9… not much chamber space if you ask me. :wink:
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Unread postAuthor: STHORNE » Mon Apr 14, 2008 9:15 am

looks like a pretty wiked design. nice work and good luck making it
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Unread postAuthor: koolaidman » Mon Apr 14, 2008 8:02 pm

Thanks guys, I will definately flip the blow gun. The friend i am making it for has quick connects on his compressor so i think all i need to do is put those .25" male connectors on the blowgun and one on the ball valve to fill the m203. Ya, i know the cv is real small, its 1:5. But, this is probably on gonna be used alongside a compressor and fired at a target at relatively close range so i dont need immense power and ping pong balls wont stay fast for long anyways.
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Unread postAuthor: koolaidman » Mon Apr 14, 2008 8:02 pm

Thanks guys, I will definately flip the blow gun. The friend i am making it for has quick connects on his compressor so i think all i need to do is put those .25" male connectors on the blowgun and one on the ball valve to fill the m203. Ya, i know the cv is real small, its 1:5. But, this is probably on gonna be used alongside a compressor and fired at a target at relatively close range so i dont need immense power and ping pong balls wont stay fast for long anyways.
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Unread postAuthor: Hubb » Tue Apr 15, 2008 11:36 am

It looks as if it is going to be a cloud type, correct? If so, it would probably benefit you to consider a vortex cap for this design. That should work well for that magazine thing you got going.

As far as the design goes, it's excellent and I am fully prepared to see what the finished product looks like. By the way, the stock looks like 1", correct? If so, where do get the wye in that size?
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Unread postAuthor: Davidvaini » Tue Apr 15, 2008 4:54 pm

hubb017 wrote:It looks as if it is going to be a cloud type, correct? If so, it would probably benefit you to consider a vortex cap for this design. That should work well for that magazine thing you got going.


Vortex Cap FTW!

A vortex cap design would look sweet with that...
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Unread postAuthor: koolaidman » Tue Apr 15, 2008 7:14 pm

hm... well thats pretty much the same design. I see how on those the hoses are perpindicular and act like a vortex block. I might consider making them enter the cap like that. Although that would it increase my rof? in that case i might keep it the way it is. Thats a 1" whye, I was planning on getting some of the pieces of flexpvc. Does anyone have a better site
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