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bbmg vortex block

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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bbmg vortex block

Unread postAuthor: c11man » Wed Mar 11, 2009 7:41 am

i am planning on making a vortex machinegun and would like some numbers on similar guns. first with 110psi what kind of fps could you expect from a average or slitly better block. also what rof will you get. and finaly how do diffrent barrel lenghts affect both. i am planning on using a modded blow gun or similart to power it
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Unread postAuthor: Stephen Holliday » Wed Mar 11, 2009 8:20 am

Check out the bbmg starfer forum for all kinds of imformation on different types of bbmgs. You can see my MP5 set up on the ready to assemble picture. I try to keep under a 14 in. barrel. This will empty 2000 bbs in less then a minute. I'm running 125 lbs. off my compressor for it.
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Unread postAuthor: jimmy101 » Wed Mar 11, 2009 12:16 pm

3 foot length of 1/4" OD (0.188" ID) stainless steel tubing for the barrel
firing 0.177" copper/steel BBs (0.33g)
Vortex type chamber
120 PSIG compressor output

Chronometer results:
ROF 50 +/-10 RPS (~3000 RPM)
Muzzle Velocity 340 +/-40 FPS
KE 1.6 J (1.2 foot-pounds) per BB
(the velocity and ROF are not consistent BB to BB or as the compressor's resevoir pressure drops.)

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Unread postAuthor: Davidvaini » Wed Mar 11, 2009 12:17 pm

Yes I wouldn't suggest going with a barrel longer then 16 inches because the initial velocity isn't high enough to constitute a barrel longer then 16 inches. You will start to actually lose velocity because of friction and other influences.

http://www.airsoftforum.com/board/Dispe ... 012&st=160

^ That link comes from AirsoftForum.com and their site is down more then its up, so just keep checking back every once in a while.

As long as you use an airsoft barrel your velocity should be pretty decent.. If you use brakeline you get a lot of blow-by and therfor lose a lot of power and they are not as efficient.

If you actually want to skirmish with the gun I would also highly suggest that you install a hopup of some kind.

I would also suggest adding a plunger for better feeding.
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Unread postAuthor: jimmy101 » Wed Mar 11, 2009 1:12 pm

Davidvaini wrote:Yes I wouldn't suggest going with a barrel longer then 16 inches because the initial velocity isn't high enough to constitute a barrel longer then 16 inches. You will start to actually lose velocity because of friction and other influences.

http://www.airsoftforum.com/board/Dispe ... 012&st=160

^ That link comes from AirsoftForum.com and their site is down more then its up, so just keep checking back every once in a while.

As long as you use an airsoft barrel your velocity should be pretty decent.. If you use brakeline you get a lot of blow-by and therfor lose a lot of power and they are not as efficient.

If you actually want to skirmish with the gun I would also highly suggest that you install a hopup of some kind.

I would also suggest adding a plunger for better feeding.

I believe all that is stongly dependent on what he intends to fire and what he intends to fire at. The OP doesn't say airsoft or copper/steel. The OP doesn't say if it is for firing at a person or ripping up empty soda cans. (Serious flaw in the OP, people please try to actually explain what you want to do.)

The best barrel length depends on the intended use, type of ammo, how well the ammo fits in the barrel, the operating pressure, the flow capabilities of the valve and hose ...
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Unread postAuthor: c11man » Wed Mar 11, 2009 4:11 pm

ok i will be firing 6mm plastic bbs at people and the barrel i barrly larger than the bb it has an inside diameter of .239 and is mcmaster part # 5560K311 and i alread told you the pressure wicth is 110 or slightly more and a flow capability of a modded blow gun.
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Unread postAuthor: Davidvaini » Wed Mar 11, 2009 6:52 pm

Alright .239 is 6.07 which is slightly tighter then an average stock airsoft barrel.. tightbores are generally considered 6.01 - 6.05. With your barrel your blowby is reduced quite a bit. Now I would not use all 36 inches because with .20g BBs in a good vortex BBMG you will get velocity reduction (friction and other sources) with a barrel longer then 16 inches. Now I would recommend you go as long as possible that is under 16 inches because of increased accuracy with a longer barrel.

In a cloud system or vortex system without a plunger or better feeding system(cloud, T-Vortex), the BBMG is more of an air suction system. Meaning that the BB's are being sucked out the barrel.. a longer barrel in a suction system will reduce BB re-chambering time which in-turn reduces ROF. I have found with tests that when you add a plunger into the mix or a better feeding system, the method of how the gun shoots changes from a suction system, to more of a forced air system in which case ROF is not changed with barrel length as much.


Now are you going to be using it for skirmishes (matches against other people)?

If so; here are the different situations for Airsoft.

CQB (Close battles, typically done in buildings or range limiting environments: - I wouldnt worry about installing a hopup or going for a longer barrel as much as I would focus on portability, shorter gun length, and increased efficientcy.

Woodland - Typically done outdoors in areas that allow long range attacks.:
I would install a hopup for increased distance and accuracy if you are going to use it in woodland. Many people dont recomend hopups in BBMGs because they will wear down too fast.. but generally speaking I have found that they actually last a lot longer then you would think and besides.. even if it gets worn down.. its the same as not having one anyways. I would also focus on getting your barrel to be around 14-16 inches. I would also recommend focusing on portability, and efficiency.


If you have any other questions feel free to ask.
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Unread postAuthor: c11man » Wed Mar 11, 2009 9:27 pm

wow took me a while to read it but that was some good advice. now all i need is a good design for a block that i would make out of plastic. could someone pleas help me with the design of a block that would be made of plastic(not sure if it matters what the block is made of) oh and it would be for close quarters as david explained so well.
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Unread postAuthor: Davidvaini » Wed Mar 11, 2009 10:51 pm

c11man wrote:wow took me a while to read it but that was some good advice. now all i need is a good design for a block that i would make out of plastic. could someone pleas help me with the design of a block that would be made of plastic(not sure if it matters what the block is made of) oh and it would be for close quarters as david explained so well.


Maybe that info should go into the wiki....eh..(my lazy day today)

make sure to taper the barrel hole so that the BB's will feed better and more smoothly to increase efficiency.
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Unread postAuthor: c11man » Thu Mar 12, 2009 7:43 am

with the barrel i know that i have to taper it but do you want the barrel sticking into the large hole or do you want it recessed into the block material? also could you provide some specifications like center hole diamber and block thickness so that i could get a gun with high fps. oh and i have changed my design and it will now run on 200psi co2 so it that changes anything could you tell me. thanks
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Unread postAuthor: jackssmirkingrevenge » Thu Mar 12, 2009 8:15 am

Davidvaini wrote:Yes I wouldn't suggest going with a barrel longer then 16 inches because the initial velocity isn't high enough to constitute a barrel longer then 16 inches. You will start to actually lose velocity because of friction and other influences.

http://www.airsoftforum.com/board/Dispe ... 012&st=160

^ That link comes from AirsoftForum.com and their site is down more then its up, so just keep checking back every once in a while.


The link is irrelevant because it refers to AEGs (not to mention containing the belief that longer barrel = more accuracy because the muzzle is a few inches closer to the target :roll: ). In an AEG, it is possible to have a barrel long enough to have a volume larger than the swept volume of the piston, in which case yes, a barrel longer than this will effectively cause a loss of performance.

However, cloud/vortex BBMGs operate on an entirely different principle, because you're feeding a constant flow of air into the barrel and in theory, the longer the barrel, the higher the velocity.

How this would relate to accuracy I detailed in a recent post elsewhere:

Long barrels are associated with long range accuracy because a long barrel usually means high velocity and this results in a flatter trajectory. The projectile gets to the target quicker and therefore has less time to be affected by gravity, wind and other environmental factors which have to be compensated for.

The other side of the coin however is that with a longer barrel, there's more time in between you pulling the trigger and the projectile leaving the muzzle, so any movement during that time is more likely to have a negative effect on your accuracy.

In short, the ideal in terms of accuracy is to achieve as high a velocity as possible from as short a barrel as possible.
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Unread postAuthor: jimmy101 » Thu Mar 12, 2009 12:49 pm

The other side of the coin however is that with a longer barrel, there's more time in between you pulling the trigger and the projectile leaving the muzzle, so any movement during that time is more likely to have a negative effect on your accuracy.

True but probably not terribly important. The longer the barrel is the less barrel transit time is added per added length of barrel. For example, The difference between a 24" and 25" barrel is the time it takes for the round to travel 1" at the muzzle velocity of the 24" barrel. That increase in time is pretty small. For a 300 FPS velocity that added inch increases the transit time by about 0.3mS, compared to the total transit time of about 13mS.

Even doubling the barrel length from 24" to 48" is only going to increase the transit time from about 13mS to about 19mS, a 46% increase in time even though the barrel inreased 100% in length. (Assumes average velocity is half the muzzle velocity and velocity scales as the sqrt of barrel length for a constant pressure air source.)

I agree with the affect of the barrel length on the velocity. With a constant air supply pressure the longer the barrel the higher the muzzle velocity. At least, up until the point where the projectile velocity approaches the maximum air velocity through the barrel.

With a constant air supply pressure friction between the ammo and the barrel doesn't limit the barrel length like it would with a constant volume air source.
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Unread postAuthor: jackssmirkingrevenge » Thu Mar 12, 2009 12:59 pm

Fair point jimmy, projectile travel along the barrel is just one component of the number of actions that happen between pulling the trigger and the projectile leaving the barrel. There's everything that happens before the projectile starts accelerating that is probably more likely to spoil your aim.
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