vortex hybrid airsoft BBMG design suggestions

[mateba]

Hello guys, first time poster. CO2/HPA airsoft user.

I would like to make a BBMG. I like the vortex block design but they have their drawbacks. Let me know if this is just wishful thinking.

I would like to use an air tight sprocket driven BB hopper similar to the P3 M134a auto-loader and feed it directly into the chamber that's in-line with the air source. I'm thinking the FPS will be more consistent and use less gas. ROF is not a huge concern here, I would rather not have the absurd performance of 100+rps. Half of that would be more than enough.

Has anyone modded a hop-up unit into a BBMG before? Any struggles to avoid? Do they just wear out to quick?
I was thinking of using 70 duro adhesive rubber patches for buckings. Essentially taping a section to the barrel, clamping it still and using a nylon tipped set screw to adjust the hop.

One of my main issues is planning out the chamber. I'm thinking of using a push-to-connect "T" fitting, but I want the BBs to stop in a vertical stack unless air is forcing them out. I don't want them rolling out of the barrel. Do you think an o-ring would accomplish this?

Do you guys have a good source to bulk BB orders or cheap rice bag purchases?

I'm very open the suggestions and any pointers if you got them.
mateba

[Hubb]

If you're looking to create a BBMG with a lesser rate or fire, try adding a detent to the barrel. This will allow pressure to build up a little bit more in the launcher (which will increase the power) but will slow the rate of fire down. If you're wondering about the increase in power being too much to use on field, this can simply be adjusted by using less initial pressure. Also, an adjustable detent would be helpful for this.

As far as homemade hopups go, it has been done to great success on several occasions. Take a look at Improving the Barrel (located in my sig). It has several ideas for detents and hopups that you should be able to incorporate and change for your needs.

Good luck with the project and welcome to Spudfiles.

[mateba]

Thanks bud. I like that hop-up design, it looks like a Sun Project HU sleeve. The o-ring detent is a good idea too. Thanks for the notes.

When you make these HU sleeves are you using these directly on the surface of the projectile or is there an additional material used, like a bucking?

[Hubb]

I'm assuming you're asking about the adjustable hopup, right? If so, I just added a layer of electrical tape to give it a little more of a grip compared to the PVC. It should also be mentioned that this particular hopup system I build was designed for golf balls and not airsoft bb. It was, however, designed after a paintball hopup known as an Apex.

Also, as far as an adjustable detent system, jacksmirkingrevenge posted a link in the same thread to a detent system he designed. That would probably work out better for you than the o-ring detent (which was really only designed to keep a projectile from rolling out the barrel).

[mateba]

I could not locate that thread jacksmirkingrevenge posted but I did see this on McMaster-Carr. http://www.mcmaster.com/#spring-plungers/=3ntxn7 Its an spring plunder in the form of a set screw. I could use this and still get a air-tight seal in my chamber. I could install this with a bushing.

[jackssmirkingrevenge]

This was the conceptual idea to create an adjustable rate of fire for BBMGs, I used the principle for a micro BBMG prototype and it worked

This project by Davidvaini might also be of interest to you, or if you're the masochistic type, have a look at my prototypes:

Modified pop-off valve

custom pop-off v1.0

custom pop-off v2.0

custom pop-off v3.0

[POLAND_SPUD]

I've been thinking of something similar for quite a long time... basically a hybrid of BBMG with a detent and valveless launcher...

so something that could fire full auto at relatively low ROF but also could fire single shots/shorts bursts and would have performance similar to a burst disk gun

[jackssmirkingrevenge]

I've been thinking of something similar for quite a long time... basically a hybrid of BBMG with a detent and valveless launcher...

Every man's dream

so something that could fire full auto at relatively low ROF but also could fire single shots/shorts bursts and would have performance similar to a burst disk gun

I flirted with the idea here, the problem is reliable feeding. When you apply a detent to a typical vortex BBMG, the interrupted flow does mess with feeding. Ideally you'd have a spring fed magazine for reliability but this in turn makes it unsuitable for sustained firing because I don't see more than 50 or so rounds per magazine being feasible.

A compromise would be to have some sort of externally powered magazine that feeds rounds from a hopper, but this adds complication.

Still on the drawing board

[POLAND_SPUD]

well you can use a simple T... basically something like davidvaini's idea or what mateba mentioned

I am only worried that an-oring might not return fast enough to its original size to stop the next round

the magazine tube could use a sort of 6mm-to-20mm tube adapter to accommodate more ammo... and I am thinking that it would be easier to keep everything compact by having the magazine tube inline with the barrel (opposite to the barrel port)



lol does it seem like a good enough idea for European Community Project ??


it could be built as a modular gun... one main part (probably housed inside an iron T ) would have threaded joints that will allow to convert it from a sub machinegun/carabine version with longer barrel to a machine pistol in a matter of seconds...

of course I am not saying that we should build one prototype only as customs would surely confiscate it...

I am talking about designing one part built using materials available everywhere that does the job

[mateba]

Thanks guys,

I'm not worried about obtaining semi-auto, at least not in this gun, I just don't want BBs to roll out of the barrel do to pressure built up in feeding system or what have you.

My feeding system will use a AEG motor driven sprocket to shuttle BBs into a channel and then into a tube or spring. I'm not sure if I'll use a spring but it would assist in a faster feeding system since the coils will stretch and retain energy like a hi-cap's clock spring. If I do not use the spring I don't think I'll have much to worry about a simple o-ring and bushing (seal the barrel again) will probably do it. Without the spring BBs will not move unless the sprocket is turning.

I might look into o-ring material, hardness and designs to see if a particular shape could lend to better performance.

As for hop-up, I thought a nylon tipped plunger spring my be worth a shot. There are two, one with 1.8-3.7lbs of pressure (soft HU)
http://www.mcmaster.com/#2191a192/=3oahcd
and two, with 4.5-7.8lbs of pressure (hard HU) http://www.mcmaster.com/#2191a182/=3oai6a

If I can disassemble them, I would install precision ground rubber balls at what ever hardness I wanted. It would be a lot nice.

mateba

[jackssmirkingrevenge]

The magazine tube could use a sort of 6mm-to-20mm tube adapter to accommodate more ammo... and I am thinking that it would be easier to keep everything compact by having the magazine tube inline with the barrel (opposite to the barrel port)

Well, I have a pressure washer handle and paintball tank that seems a waste to use on a 4.5mm BBMG. Picture double that calibre, then a 20 round magazine in line with the barrel would provide a worthwhile weight of fire... hmm...

[POLAND_SPUD]

so your talking about 9mm right ?? that would pack more punch per one bullet but you are limited to ball-bearings only

5.6mm and 6mm are quite common and available in various weights... ( the only problem is that right now I have 6mm ammo and 5.6 barrel )

steel 6mm BBs are 0.8g each - lead are probably around 1.1g - I reckon it's enough for a full auto

then a 20 round magazine in line with the barrel

20 rounds hmmm that's only 2 seconds at 10RPS

I wants 10 second bursts... lol

I've been thinking of something like this (that's just a very rough sketch) ->

[jackssmirkingrevenge]

You're going to have to put a bit more thought into it, if it worked this way then no one would bother with vortex blocks...

The magazine tube would have to be less than twice the diameter of one BB, otherwise you need some mechanical means (say a motor driven paddle) of agitating the BBs for reliable feeding.

so your talking about 9mm right ?? that would pack more punch per one bullet but you are limited to ball-bearings only

That's the basic idea, you don't need to worry about large magazines because you can destroy the target with less rounds.

20 rounds hmmm that's only 2 seconds at 10RPS

I wants 10 second bursts... lol

Say you're using a 50cm barrel, you could have a 50 round 0.5" wide tube magazine + spring fit comfortably. Also, 10 round per second is still a bit high, I would be happy with 2-5 (DAKKA DAKKA DAKKA, remember )

That's for 9mm though, a 50cm barrel for 6mm ammunition gives you at least 75 rounds easily in a parallel magazine

[POLAND_SPUD]

agitating the BBs for reliable feeding

actually I was thinking that in each 'cycle' the plunger (if it was tight fit) would move slightly forth and back thereby agitating BBs

but yeah I have to agree that your idea is probably simpler