SpudFiles

why not just try one? it could turn out really good.

I actually just did, and a small plastic ball penetrated approximately twice as far into a book with the butane than without. Of course, it may have been how the book was sitting, but the second shot definitely went off with more of a bang...

So what it appears I've created, is a hybrid which is easier to fire than a spray'n'pray... it goes off EVERY time, though whether the butane drastically increases performance or not all depends on luck when fuelling, and the pressure used (which of course affects the mix).

One interesting little thing which I discovered though, was that the combination of a clear burst disk and a rather bright electric arc right next to it when firing, meant that the plastic projectile, which happens to be made out of glow in the dark plastic, glowed extremely well for a few seconds after firing... the arc in the chamber had charged the glow at the instant of firing! This should be fun at night!

You think this would work on a larger scale? I could give it a go this afternoon with my hybrid. I use a sparkplug for electrodes and 100kv stungun for ignition.

Insomniac wrote: yes, it is using a clear burst disk. How could you tell?

i was looking at the bright circle of light on the wall and thought it had to be and just wanted to know if i was right

Insomniac, you may be on to something, I would still like a picture of your setup no matter how simple if you can get one. How high of voltage do you think is necessary?'

also, Insomniac, you should start a new thread on this, we are majorly hi-jacking ATM

Hahah I know how you could tell

And Crowley, I see no reason why it wouldn't work on a larger scale, but I suspect that there are a few conditions which have to be met before it will...

First off, the spark probably has to be rather close to the burst disk... Due to my tiny chamber, the spark is only a cm or two behind the disk, meaning that bits of flaming metal are practically guaranteed to hit it. (Perhaps you could use some coat hanger wire or similar to extend the electrode of your spark plug, and use the chamber wall as your second electrode).

Second, the burst disk will probably have to be something that flaming bits of metal are going to puncture... I'm using one layer of sellotape, so it's not particularly resilliant to heat.

Third, the disk ought to be close to it's failure point... I was trying to make it fire with nothing but butane in the chamber (using the butane's ~90psi vapour pressure to burst the disk) but it wouldn't go off. It only seems to work when pressurised to around 200 psi... The disk tends to burst on it's own at ~230 psi.

Lastly, I don't think a stun gun is capable of vapourising aluminium foil... You need capacitors to make a nice arc which sends sparks flying.

EDIT: http://www.spudfiles.com/forums/viewtop ... tml#299261 Here we go.

Insomniac wrote:True, but I'm sure over 95% of the guns people build here serve no true purpose... they are just little engineering challenges which are fun to use after they've been built. So the answer to 'Why make cartridges at all?' is 'Why not?'

I keep telling him, but he won't listen

yeah but you've got to have a mag large enough to fit as many cartridges as you want to get shots. so if you want to get more than 10-15 shots then the size and weight of cartridges might be greater than the size and weight of automated metering system...

- on board propane tank + regulator
- on board compressed air tank + regulator
- inlet valves
- non-burst disk valve system
- ammunition supply and magazine

Surely for the weight and bulk of the above, you can just carry a few spare 10 round magazines

also don't forget that you have to fill and load cartridges too

I spend more time reloading my Monsoon mags than I do shooting them off, it's still the box deluxe though And really, once you get use to it, takes no time at all.

still you're somewhat limited by the size and weight of cartridges

You're limited in mag capacity, but what doesn't fit on the launcher itself can be carried as spare mags, hell why not

you need a standalone metering station

What - a blowlamp, syringe and shock pump? You make it sound like an oil rig!

Don't get me wrong, I would love to see a self metering hybrid feeding ammunition from a magazine and potentially full auto - but that's your job, DCV boy

you make a much better argument then i do JSR but that pretty much sums up what i was trying to say

ilovefire wrote:but that pretty much sums up what I was trying to say

I think this sums it up even better though note that the above argument was made without reference to the rule of cool, which ultimately is my main justification for cartridges

jackssmirkingrevenge wrote:

ilovefire wrote:but that pretty much sums up what I was trying to say

I think this sums it up even better though note that the above argument was made without reference to the rule of cool, which ultimately is my main justification for cartridges

yes that is also a big part of it, pity im to lazy to make a mag for the gun im making its just going to be a one shot bolt action with an integral suppressor

If lazyness is the issue, it's probably easier to have the cartridge eject automatically on firing than make a locking bolt action...

jackssmirkingrevenge wrote:If lazyness is the issue, it's probably easier to have the cartridge eject automatically on firing than make a locking bolt action...

sure but then there is the large possibility of the cartridge being damaged on ejection, there could be a power decrease and also on with a suppressor that is is really going to be bad for performance, and the build would be a bit more complicated and would increase the chance of me not finishing it, but maybe in the future if i feel like something else to do i might convert it or make a new one but for now i think ill be happy with what im planing on making

Fair enough, but bolt action ejection means you're going to have to add a cartridge rim and extractor claw of some sort, unless you're just going to tip the cartridges out.

Back to the subject of this thread, finally got some velocity data with the long 6mm barrel, not as dramatic an increase as I expected but impressive nonetheless:

0.22" 16 grain pellet (flared out to fit barrel) - 1049 fps - 39.1 ft/lbs

0.25g airsoft BB - 1096 fps - 10.3 ft/lbs

0.12g airsoft BB - 1179 fps - 5.7 ft/lbs

As to the cartridges, while the mini works, I'm still not willing to let go of the potential benefits of having a friction seal instead of a burst disk.

Perhaps having the BB already in the seal on pressurising is a bad idea, and I should change the configuration, maybe with an o-ring instead of a tubular seal.

jackssmirkingrevenge wrote:Fair enough, but bolt action ejection means you're going to have to add a cartridge rim and extractor claw of some sort, unless you're just going to tip the cartridges out.

yea, is there something wrong with "just tipping it out"?

jackssmirkingrevenge wrote:Back to the subject of this thread, finally got some velocity data with the long 6mm barrel, not as dramatic an increase as I expected but impressive nonetheless:

0.22" 16 grain pellet (flared out to fit barrel) - 1049 fps - 39.1 ft/lbs

0.25g airsoft BB - 1096 fps - 10.3 ft/lbs

0.12g airsoft BB - 1179 fps - 5.7 ft/lbs

what were the mixes that you were using?

jackssmirkingrevenge wrote:As to the cartridges, while the mini works, I'm still not willing to let go of the potential benefits of having a friction seal instead of a burst disk.

personally i think it is more trouble then it is worth because it is going to be really fiddly to get it right, on just one then you have to make more, also with the friction and heat i would think there would be a lot of wear so the power would slowly decrease and fixing it would be a pain

ilovefire wrote:yea, is there something wrong with "just tipping it out"?

Well, it works - but there's a certain je ne sais quoi about pulling back the bolt and seeing the extractor kick out the cartridge

what were the mixes that you were using?

All done at 14x

personally i think it is more trouble then it is worth because it is going to be really fiddly to get it right, on just one then you have to make more, also with the friction and heat i would think there would be a lot of wear so the power would slowly decrease and fixing it would be a pain

Ne'er a truer word spoken, but I want to make sure I've milked the idea before putting it aside. In that regard, I've just come back from the hardware store with my weekly (:roll:) supply of Araldite and $5 worth of o-rings in various sized