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DV's Official Tips For Vortex 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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DV's Official Tips For Vortex BBMGs

Unread postAuthor: Davidvaini » Thu May 07, 2009 2:57 pm

DV's Official Tips For Vortex BBMGs:

Use a barrel that is very close to the size of the projectile. Try to minimize blowby as much as possible. If you are making an airsoft vortex BBMG, make sure to use an airsoft barrel, brakeline has way too much blowby which reduces power and efficiency.

Always have a spring and a plunger, If you cant find a spring, shop online, if you cant shop online, then ask a friend to shop online, unless your country has laws against springs there should be no excuse.

As far as the spring strength, make sure to get a spring that is just strong enough to push the bbs to the vortex block. If the spring is just strong enough then you will not need a shroud. If you couldn't find a spring with just the right amount of strength, then put a shroud or skirt on the top of the vortex block.

When installing the barrel to the vortex block make sure to file the inlet to the barrel so that it "funnels" into the barrel(this will allow for better feeding efficiency). Also make sure to match the beginning of the barrel to match the curvature of the vortex hole.

For the air inlet, either have the hole for the air inlet be smaller than the projectiles or add a screen to prevent BBs to fall back into your air stream.

If you are using a vortex BBMG for airsoft and you want greater range and accuracy, you can install a hopup. For the longest time there was the notion that it would be silly to add a hopup because it would wear down to fast. This really isnt that true, it doesn't really wear down too fast. Even if it did wear down, you are roughly in the same boat as you would be without a hopup. A hopup is the number one part of a BBMG or airsoft gun that improves range. A hopup when dialed in correctly will also help with accuracy.

Note: This is an on going thread about helping people improve their BBMGs.
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Last edited by Davidvaini on Sat Jul 23, 2011 8:16 pm, edited 2 times in total.
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Unread postAuthor: jrrdw » Thu May 07, 2009 4:08 pm

Thank you David, this will be a great help. :D
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Last edited by jrrdw on Thu May 07, 2009 7:29 pm, edited 1 time in total.
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Unread postAuthor: thedeathofall » Thu May 07, 2009 5:15 pm

Don't forget to add that ammo weight/size can also increase accuracy and damage. Unless you're using the gun for airsoft, you will get better damage results and more accuracy from metal bbs.

Other than that i think this is a great idea David. Keep it up
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Re: David Vaini's Official Tips For Vortex BBMGs

Unread postAuthor: jackssmirkingrevenge » Fri May 08, 2009 12:42 am

Davidvaini wrote:Use a barrel that is very close to the size of the projectile. Try to minimize blowby as much as possible. If you are making an airsoft vortex BBMG, make sure to use an airsoft barrel, brakeline has way too much blowby which reduces power and efficiency.


This point is worth emphasising, I had done an experiment back on spudtech to try and quantify the effect of barrel tightness here.

A difference of 0.5mm (0.02") was enough to cause a significant power loss.

Playing with feed/barrel positions is definitely not going to increase power. It might give you better reliability, but it won't help with efficiency.

You can improve performance by dramatically increasing input flow (say using a 1/2" ball valve instead of a blowgun) or pressure (800 psi is definitely recommended, in theory energy increase should be about linear with pressure) but that doesn't make it more efficient.

One solution is to put some sort of detent (for example an o-ring seal, magnet in the case of metal BBs or a spring loaded ball detent) that will hold the BB at the breech allowing pressure to build up in the BB chamber before the BB is released. It also has the added benefit of reducing rate of fire to some extent making your design more economical with BBs.

Another solution, not as ergonomical as the blowgun but it works for power, is to have the BBs already inside a pressurised chamber and having a ball valve between the chamber and the barrel through which the BBs will flow.

Image

This means that if your input pressure is 80 psi, that BB will definitely have 80 psi behind it as it fires, as opposed to around 25% of that which a conventional blowgun fed strafer design will give you.
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Last edited by jackssmirkingrevenge on Tue Feb 16, 2010 2:49 am, edited 2 times in total.
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Unread postAuthor: littlebro05 » Fri May 08, 2009 1:03 am

That sucks man... the only thing I have closest for a barrel is a brakeline (and not even I know I can buy it yet) I don't live jackall hobby shops either. Does anyone knows the ID of a 5/16" Brakeline, while we're still on barrel topic. It's cause it's probably the closest thing I can get for an aluminum barrel since Bic pens have like a mega blowby with a diameter of 7mm and their lopsided like hell.

Love to live in Australia :(... one thing I always need they don't have.
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Unread postAuthor: CpTn_lAw » Fri May 08, 2009 4:28 am

Barrel diameter should be one of the most important things. I 've been playing airsoft for quite some time now, and i can assure you that even a 6.1 mm barrel is too lose for BB's. If you want an airsoft barrel, make sure you have a 6.04 - 6.03 I.D. barrel.

Hop-up increases range and accuracy, as the spin-back gives an inertial stability to the BB, and it's much less likely to be deviated.


You also want heavier BB's. 0.2 gram is too light, for a 400 fps gun (with 0.2), i'd recommend using 0.28 gram BB's. you'll lose a little in initial velocity
but you'll gain in range, kinetic energy, and accuracy.
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Unread postAuthor: Davidvaini » Wed Apr 13, 2011 12:35 am

bump

simply because I have seen a lot of newbies not following these simple rules recently.
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Unread postAuthor: Mc Frown » Thu Apr 21, 2011 11:23 pm

most of the time it's because they dont have access to materials or are cheaping out a proof of concept before going all in
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Unread postAuthor: Lockednloaded » Fri Apr 22, 2011 12:20 am

I recently put together a simple cloud, just for the hell of it, but I was surprised at the power when using a 6.02mm airsoft barrel. A hint when using airsoft barrels, put the side that has the slight inner taper on the chamber side to aid in feeding
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Unread postAuthor: Gun Freak » Fri Apr 22, 2011 9:43 am

I ordered a 650mm 6.03mm barrel for my airsoft project, how do you think the accuracy will be with a .2? If it sucks with .2s I might go for some .28s.
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Unread postAuthor: Davidvaini » Fri Apr 22, 2011 12:03 pm

Gun Freak wrote:I ordered a 650mm 6.03mm barrel for my airsoft project, how do you think the accuracy will be with a .2? If it sucks with .2s I might go for some .28s.


That depends on a lot of things. First and for most is do you have a hopup? Without a hopup your accuracy is thrown out the window from the start.

Hopup applies backspin causing the spherical projectile to be more stable, and have a straighter trajectory. It also is a huge player when it comes to range for this same reason. (causes the bb to fly straighter farther.)

Next would be velocity. If you stick .20g bbs in a 600fps gas sniper rifle, the bb's are gonna fly all over the place. The weight can simply not handle the air resistance at that velocity.

.20 - .25 are the minimum you should go with an airsoft gun. After some testing, even with my cyma glock AEP that shoots .20's at 220fps, when I put some .25g bbs In the performance seemed to increase without having a general affect on range. But when I tried .28g the range suffered. (btw I did adjust the hopup each time to act accordingly to the velocity - a lot of people will not do this which is stupid.)

I am a firm believer that the general airsoft public uses too light of BBs. Back in the day people used .12's and when .20's came out people were amazed at the improvement of accuracy so much. .20s became the popular ammo choice. For a while there .20g were the heaviest you could get, so after time .20 came the preferred weight. Even when heavier BBs came out .20 were cheaper and most people still had thoughts of, this is almost double the weight of the original airsoft bb and I dont think I should go heavier. .25 might be a tad heavy... In fact I beleive that .20 are a tad light, and .25 more towards the weight that should be used.

As your velocity increases, I typically suggest increasing the weight of the BB if accuracy is important to you. If my 220fps (@.20) glock shoots fine with .25's, can my 400fps(@.20) shoot heavier? of course it can.

I find that testing a gun by putting in heavy BBs and adjusting the hopup as heigh as i can helps. If the bbs are dropping at this point or the gun is jamming, use lighter BBs, if the hopup is still causing the bbs to curve up, then get heavier bbs. Most people will adjust the hopup down, but the fact that the heavy bbs are still curving up gives you an idea that you could use heavier BBS to straighten your trajectory rather than simply lowering the amount of backspin. Once you find the right area where you get a nice straight trajectory with good range, then you are in the "golden zone". Now going with too heavy of BBs can affect your range obviously, sometimes you will get a straight trajectory with say .28g bbs but the range is 30 feet less than with .25g bbs.. The .28g will be more accurate up to its max range, but the .25 shoot further. It is about finding the right mix that suits your style of play.


So to wrap it up:

Things of importance for accuracy:
Hopup
Hopup
weight of BB
consistency of velocity
barrel quality and tolerance.

Things of importance for for range:
Hopup
Hopup
velocity
weight of BB
barrel length, quality and tolerance.


Edit: can we get this stickied?
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Unread postAuthor: JDP12 » Fri Apr 22, 2011 12:34 pm

David- do you have any recommendations on a hopup design?
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Unread postAuthor: Gun Freak » Fri Apr 22, 2011 12:34 pm

I think hop up might have to be incorperated then. I wasn't planning on it, but the portion of the barrel with the hole for the hop up is exposed, but there is not enough room for a hop up unit. The closest thing I might be able to fit in there is a few wraps of electrical tape. Yes it is serviceable. The gun I am making might have a rather high rate of fire, though, which is why I didn't want to waste money on heavy bb's... Just for clearification, it is a 650mm 6.03mm Madbull Black Python.
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Unread postAuthor: Davidvaini » Fri Apr 22, 2011 3:49 pm

JDP12 wrote:David- do you have any recommendations on a hopup design?


honestly using a hopup chamber from an airsoft gun, a decent one like a m14 hopup from a Cyma or a TM based m14.. lots of adjustment, and works with airsoft barrels
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 24, 2011 11:48 pm

Davidvaini wrote:Hopup applies backspin causing the spherical projectile to be more stable, and have a straighter trajectory.


Hop-up isn't there for stability, the gyroscopic effect is not along the same axis as that applied to a bullet fired from a rifled barrel but rather is tangential to the line of flight. What hop-up does is trade velocity for lift through the magnus effect.

Image

Davidvaini wrote:Things of importance for accuracy:
Hopup
Hopup
weight of BB
consistency of velocity
barrel quality and tolerance.


High velocity is also an important factor for accuracy, indeed it would be much better to fire heavy BBs at high velocity than to have hop-up. The latter is required because of the low velocity and woeful sectional density of airsoft BBs which give them a howitzer-like trajectory at anything past a few yards range.

I understand that if you want to have an airsoft gun for skirmishing, safety considerations will limit the performance, but otherwise stress should be made on obtaining the highest possible velocity with the heaviest possible BB. The former will ensure a flatter trajectory and shorter time to target, while the latter gives better velocity retention due to high sectional density while making the projectile less vulnerable to environmental factors.

The importance of barrel tolerance cannot be overstated, the "golfball in a drainpipe" analogy applies here.

Davidvaini wrote:Things of importance for for range:
Hopup
Hopup
velocity
weight of BB
barrel length, quality and tolerance.


Barrel length in itself will not give you longer range, it is the higher velocity usually supplied by a longer barrel that contributes to this. However, if you can achieve velocity without resorting to a longer barrel, this is better in terms of accuracy. Essentially it means that the time interval between trigger being pulled and projectile leaving the muzzle is shorter, so there is less time for gun or target movement during this delay to be a factor.
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