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adjustable rate of fire for BBMGs?

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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Unread postAuthor: Antonio » Wed Apr 02, 2008 11:56 am

When the barrel lenght is increased the pressure difference between the air reservoir and the end of the barrel is the same. U do loose some pressure bc of friction allong the inside of the barrel, but this is really small.
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Unread postAuthor: littlebro05 » Thu Aug 07, 2008 8:51 am

ant wrote:When the barrel lenght is increased the pressure difference between the air reservoir and the end of the barrel is the same. U do loose some pressure bc of friction allong the inside of the barrel, but this is really small.


HOpefully not bringing up an old topic but it seems rather recent. If you the detent the other way around you will most probable produce a backspin like shown here

producing a backspin in BBMG's seem's like a fundamental of these types of guns because they seem to curve alot after the bb exits the barrels (depends on what grams you use). Any opinions? i've read through it but if you put the detent the way in the diagram it will produce a forward spin which will make the projectile drop. I'm nto sure but it seems right... any objections at this point, I'm probably wrong though but its what i'm thinking.
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Unread postAuthor: jackssmirkingrevenge » Sun Feb 08, 2009 9:48 am

I've taken a break from auto-pistons for the time being and decided to prototype this design, here's a little photo of the work in progress. It's being held by araldite for the time being but it now needs a chamber and the casting will also reinforce the detent mechanism. Who knows, this might achieve DAKKA DAKKA DAKKA! using much less mechanical complexity :)
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Unread postAuthor: grock » Sun Feb 08, 2009 8:06 pm

when im playing airsoft, i usually have to turn the FPS down by reducing the flow into the gun, it seems like that has an effect on the ROF too. but that also means that if you turn down one, the other goes down as well though.
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Unread postAuthor: jonnyboy » Sun Feb 08, 2009 9:43 pm

I would have mounted it onto the top, that way the bb won't fly into the ground.
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Unread postAuthor: jackssmirkingrevenge » Mon Feb 09, 2009 12:26 am

grock wrote:when im playing airsoft, i usually have to turn the FPS down by reducing the flow into the gun, it seems like that has an effect on the ROF too. but that also means that if you turn down one, the other goes down as well though.


In this case, you can theoretically reduce ROF without altering the flow, and the fact that you're restricting the flow at the breech before enough pressure builds up and the BB is fired, FPS should actually thereofre go up.

I would have mounted it onto the top, that way the bb won't fly into the ground.


I took the photo at that angle to show the ball detent, it's top-mounted in the chamber. Testing to be carried out in less than 24 hours ;)

edit: just realised I hadn't updated this, testing wasn't a huge success in that the rate of fire was still too high for individual projectiles to be discerned, so much for "dakka dakka dakka" :roll:
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 23, 2011 1:29 am

I've been experimenting with different ways to add detents, these are a couple of systems which I found to work well. The first one can be adjusted for strength by altering the proximity of the end of the binding to the ball, the closer it is the more pressure needed to pop the projectile. The disadvantage of this method is that some air is lost past the detent on firing, but in practice this should be negligible, all the more so if the breech is inside a BBMG chamber and there's pressure keeping it shut.

The second system is not really adjustable (unless you have different types of tubing to play with) but it prevents air loss past the detent.
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Unread postAuthor: Crna Legija » Wed Feb 23, 2011 8:35 am

wouldn't the ball just fall out?
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Unread postAuthor: POLAND_SPUD » Wed Feb 23, 2011 8:51 am

Have you tested the system that I use? (a rubber washer sandwiched between two threaded fitting)
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Unread postAuthor: mark.f » Wed Feb 23, 2011 9:22 am

-_- wrote:wouldn't the ball just fall out?


Notice the stepped hole. The part most of the ball sits in has a larger inside diameter than the very bottom of the hole (where the "active" part of the ball pokes through).

Easy enough to do with two drill bits and a drill. Even easier with a drill press. :wink:
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Unread postAuthor: Crna Legija » Wed Feb 23, 2011 9:35 am

ahh yea wasn't looking hard enough
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 23, 2011 10:55 am

-_- wrote:wouldn't the ball just fall out?


Mark explained pretty well why it wouldn't, and how to make the right hole ;)

Have you tested the system that I use? (a rubber washer sandwiched between two threaded fitting)


Yes, and I think that is the best way to go about it. An o-ring detent is easily adjustable, servicable and provides projectile retention and and airtight seal.

These are just suitable alternatives for those thinking outside the box :)
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