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High Pressure BBMG concept

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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High Pressure BBMG concept

Unread postAuthor: jackssmirkingrevenge » Sun May 03, 2009 2:08 pm

I was on the verge of completing the last in my series ofreciprocating valve automatic prototypes, however I realised that now that I have high pressure on tap, the original reason for these designs - to make the most of compressor pressures - has now been removed. In this respect, I've been thinking along the lines of a "conventional" BBMG making the best use of my resources.

I have added to the design however a ball detent which effectively makes this also a "pop-off" design. By adjusting the detent one can achieve a minimum pressure required for the projectile to be able to escape it, so by seperately regulating the airflow into the chamber - ie the rate at which this minimum pressure is achieved - one can effectively adjust rate of fire to a managable figure in terms of projectile economy.

I've made a rough prototype along these lines, the power certainly seems to be there but without a vortex block it is apparent that reliable feeding is difficult, so a version 2 is in order :)
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Unread postAuthor: Hotwired » Sun May 03, 2009 3:33 pm

Two things seem to be working against each other there:

1) You need airflow through the chamber to suck the pellets into the barrel

2) You won't get the airflow until a pellet stops blocking the barrel by overcoming the sprung ball.

Could mean less balls in the barrel at once but also less reliability in feeding.
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Unread postAuthor: ammosmoke » Sun May 03, 2009 3:33 pm

Ohhh. Hey that makes a lot of sense! If you don't mind, I just might have to copy that idea... Lol. Except I think that I will just use an inline popoff valve and use a harder spring than what comes with it.

EDIT: Wait a second, that thing blocks the pellets?? Why don't you just have a popoff restricting the airflow until your pressure comes back up? Oh wait... That doesn't make sense. EEhhhh I lost myself.
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Unread postAuthor: al-xg » Sun May 03, 2009 3:41 pm

I think the chamber is fine as it is.

But I do somewhat agree with 2), the detent could actually waste air in this case.
But then again, the hop up on my vortex strafer acted in a similar way, and it worked fine, maybe it used more air, but it slowed the ROF down (and increased accurate range)

How hard is it to open the blowgun at high pressure ? (although I'd imagine you're not running 850psi through it ?)
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Unread postAuthor: POLAND_SPUD » Sun May 03, 2009 4:00 pm

lol I knew it!! I knew you'd build a BBMG... that was just amatter of time

do you plan to place the tank horizontaly and/or use it as a stock ??
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Unread postAuthor: Davidvaini » Sun May 03, 2009 6:37 pm

this is essentially the same thing as installing a vortex BBMG with a hopup unit....
The hopup acts the same way as the spring ball detent.
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Unread postAuthor: POLAND_SPUD » Sun May 03, 2009 7:11 pm

@davidvaini lol when I was writing my post I was considering suggesting him to use your idea for at least 10 minutes before I decided not to write it...

I know I may sound like a retard or somethin but I find it uber weird that you commented next and you wrote exactly what I wanted to write


now my only question is -> is it possible to use a hop-up with a magazine ?
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Unread postAuthor: Davidvaini » Sun May 03, 2009 8:15 pm

of course, my direct feed concept does exactly that. It uses the feeding tube of the hopup to feed.

EDIT 1000'th post baby!
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Last edited by Davidvaini on Thu May 07, 2009 2:43 pm, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Sun May 03, 2009 10:14 pm

Hotwired wrote:Two things seem to be working against each other there:

1) You need airflow through the chamber to suck the pellets into the barrel

2) You won't get the airflow until a pellet stops blocking the barrel by overcoming the sprung ball.

Could mean less balls in the barrel at once but also less reliability in feeding.


These were my initial thoughts but on reflection it doesn't seem contradictory. You get BBs agitated until one gets sucked into the barrel and flow stops, it eventually pops at which point you get airflow again and the cycle continues. Considering the rate of fire of standard BBMGs it shouldn't be a long interval between a BB firing and another getting sucked in.

al-xg wrote:How hard is it to open the blowgun at high pressure ? (although I'd imagine you're not running 850psi through it ?)


I tried it at around 500 psi and it was fine, not exactly a hair trigger but reasonable. I doubt that I'd turn it up to 850 though, we'll see :)

POLAND_SPUD wrote:lol I knew it!! I knew you'd build a BBMG... that was just a matter of time


I know, I know :D

POLAND_SPUD wrote:do you plan to place the tank horizontaly and/or use it as a stock ??


Assuming it works, there's three options I'm considering:

1) As per diagram with the tank vertical, forming a hand grip to give a MAC style launcher

2) Tank horizontal base forwards Theoben Rapid style

3) Tank horizontal regulator forwards Logun S16 style

At the moment I'm inclined towards 2) as it can be made as a bullpup with the valve at the rear and a mid-placed pistol grip and rod to the trigger which would be the most compact configuration.

Davidvaini wrote:this is essentially the same thing as installing a vortex BBMG with a hopup unit....
The hopup acts the same way as the spring ball detent.


Basically, though in this case the hopup has to hold back 500 or so psi ;)

I was looking at airsoft magazines actually but 6mm sucks as a destructive calibre without a readily available supply of heavy hard ammunition, so 0.177" it is :) I've pretty much finalised the design in my head, watch this space ;)
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Unread postAuthor: SPG » Mon May 04, 2009 8:01 am

So years and years of design and development down the tubes cos you bought yourself an HPA tnak?

:roll:

jackssmirkingrevenge wrote:I was looking at airsoft magazines actually but 6mm sucks as a destructive calibre without a readily available supply of heavy hard ammunition, so 0.177" it is :) I've pretty much finalised the design in my head, watch this space ;)


I can get 6mm steel BBs here in France at airsoft (should that be airhard?) suppliers, can't you get them over there in *§#~¤ ???
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Unread postAuthor: jackssmirkingrevenge » Mon May 04, 2009 10:00 am

SPG wrote:So years and years of design and development down the tubes cos you bought yourself an HPA tnak?


In a nutshell. Sad isn't it? :roll: I'm really kicking myself for not having got an HPA bottle sooner. Still, I don't think all that R&D will go to waste, I still want a marble autocannon :D

I can get 6mm steel BBs here in France at airsoft (should that be airhard?) suppliers, can't you get them over there in *§#~¤ ???


Here in *§#~¤ airsoft tends to be played in urban settings, I've never seen an airsoft sniper rifle for sale and the heaviest BBs I can find are 0.25g. I could get steel or aluminium ones from overseas but it would be expensive, plus customs would likely take a dim view on something that looks like it would fit nicely in an improvised claymore mine, I don't like drawing attention to myself.

*trots off happily to the workbench*
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Unread postAuthor: al-xg » Mon May 04, 2009 12:30 pm

Look for "slingshot" ammo instead, they sell 6mm steell BBs.
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Unread postAuthor: ALIHISGREAT » Mon May 04, 2009 2:32 pm

customs would likely take a dim view on something that looks like it would fit nicely in an improvised claymore mine


so they would look dimly upon nuts, bolts, nails and marbles too :wink:
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Unread postAuthor: jackssmirkingrevenge » Mon May 04, 2009 10:43 pm

ALIHISGREAT wrote:so they would look dimly upon nuts, bolts, nails and marbles too :wink:


F'r chrissakes man, this is the Western world, not the Gaza Strip - we do things properly :D

al-xg wrote:Look for "slingshot" ammo instead, they sell 6mm steel BBs


Still expensive stuff to be putting through an auto...

After some experimentation, I'm not sure if a vortex block really is the way to go, perhaps a spring-loaded mag like this one proposed by SubsonicSpud would work better:

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Unread postAuthor: Ragnarok » Mon May 04, 2009 10:51 pm

jackssmirkingrevenge wrote:F'r chrissakes man, this is the Western world, not the Gaza Strip - we do things properly

He does have a fair point. A shipment of what are basically ball bearings isn't going to attract much attention - they're standard enough engineering parts.
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