The BBM rapid-fire BB gun

Building or modifying BB, Airsoft, and Pellet type of guns. Show off your custom designs, find tips and other discussion. Target practice only!
squib
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Wed Jun 03, 2020 10:37 am

This one is just a fun experiment to answer a question that's been nagging me for over 30 years. Demonstration is at the end.



CamouflageYVR
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Thu Jun 04, 2020 12:45 pm

Wow. That's a detailed video. Nice job!
Doc j
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Fri Jun 05, 2020 7:12 pm

Doc j
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Fri Jun 05, 2020 8:18 pm

Sorry last didn't attach pic
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Doc j
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Fri Jun 05, 2020 8:25 pm

In keeping with same I'd barrel throughout.
Could design be as in pic that follows.
Holes in barrel with sleeve over holes.
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squib
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Fri Jun 05, 2020 9:22 pm

Yes, however back pressure could present some headaches such as all the BB's in the magazine blowing to the rear every time a BB enters the breech, then all sucked forward again as the fired BB clears the muzzle. They would alternate back and forth with a little farther to travel every time one is fired. I couldn't come up with a simple solution for that potential issue right off so I worked around it with a gappy barrel to avoid backpressure altogether. Perhaps a check valve on the end of the rear of the magazine tube could help a bit.
squib
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Fri Jun 05, 2020 9:55 pm

I should also mention that I did try a short tube one size smaller (5/16") at the muzzle end of the barrel, a "choke tube" of sorts, in attempt to tighten the spray pattern lol . Unfortunately, even this small restriction rendered it inoperable.
Doc j
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Fri Jun 05, 2020 11:10 pm

squib wrote:
Fri Jun 05, 2020 9:55 pm
I should also mention that I did try a short tube one size smaller (5/16") at the muzzle end of the barrel, a "choke tube" of sorts, in attempt to tighten the spray pattern lol . Unfortunately, even this small restriction rendered it inoperable.
What about this?.
Have a flair entry into barrel with sleeve to cause the coanda effect of suction like the air amplifyer nozzle.
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Sat Jun 06, 2020 12:06 am

Yeah I thought about this too.
And then back pressure thing too.
Used both sorta concepts of suction when worked on drill Rigs mineral exploration. 20 years
1st one.
Like how you designed used in mixing powders with liquid.
Instead of air, used water powered from pump.
The inner creates suction of air. was connected to clear tube, that can then suck powder. It gets mixed with water.
2nd was air core , when drill clays, sands weathered rock. Like a big vacuum set up, sucks the sample dirt, etc...has a outer rod with a inner tube, air goes on outside between the two. When gets down a drill bit, there is a trumpet design and small gap, like the air amplifier nozzle. Allows the sample to get sucked up the inner tube, up to surface into cyclone catcher into a sample bag collection set up.
I don't think there was much suction external till wat ever gets right into the venturi zone.
It had plenty of punch once stuff gets into system if that makes sense.
Might add, by observation. That like in your setup.
If air acts like water,
When the pressure goes around the inner tube causes a spiral vortex, helps the suction in middle. It was noticeable with the liquid coming outa end under pressure.
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Sat Jun 06, 2020 12:10 am

worked on drill Rigs mineral exploration. 20 years .

Typo, 20 odd years ago.
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Sat Jun 06, 2020 5:50 am

squib wrote:
Wed Jun 03, 2020 10:37 am
This one is just a fun experiment to answer a question that's been nagging me for over 30 years.
That's what this forum is for, thanks for posting!
hectmarr wrote:You have to make many weapons, because this field is long and short life
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