Airsoft ordinance, discussion and theory

[cloakndagger]

Over the past few months ive been frequenting the pages of paintballers, punkin chunkers, spud gunners, and air fannoneers on a quest for information which might lead to the construction, or at least the understanding of ideal airsoft ordinance. Here is what ive found.

12g Co2 powered cannons, and Co2 saftey.
Your standard airsoft bazooka, whether mfg. by a company or built in your garage, is more often than not powered by the lowly 12g co2 cartridge.. But what many dont realize is the absolute power these little guys can carry. Co2 in a 12g cartridge is stored as a liquid, meaning whether you have a 20lb tank, or a 12g cartridge, the pressure (at 77 degrees f) is goint to stay a constant 852.68psi until you run out of liquid... Wow... Thats serious poundage!  What that means is you have to have an accumulator to bring down that pressure to a useable pressure and volume. I shoot for around 125-160 psi, meaning a 1"x4" accumulator+valve space etc.. this is "safe", but also provides you with more air volume, because you want to fill your barrel as quickly as possible.  How much volume do you need? Well it all depends, but when using high pressure gasses like co2 id err on the side of caution. Why? Well i came across several horror stories of mishaps with galvanized and pvc firing systems in my research, which is why you wont see any of my zookas sporting a co2 constant air system and 20lb tank. All it takes is a slow tiny air leak, and you have a bomb next to your head, capable of going all pvc grenade on you and your buddies.. once again, volume saftey, or at the least use overpressure release valves.

This being said, air cannons, run off of compressed air are very successful performers, reaching a max of 300meters. You must note we have left the realm of co2 for a sec, to show you what youre capable of if yoire willing to put up with a huge accumilator 2x barrel volume or more. 12g co2 cannon are generaly accepted as having a range no greater than 100 yards of semi direct aimed fire at absolute best. The majority of my sources say even wjth ideal projectiles, accurate fire past 50yds is hopeless. These are chuckkers and cannon for cryin out loud.

There is another class of launcher, combustion, that i wont delve into yet, as ive not yet built working models, except to say that theyre cheaper to build, and will outperform 12g co2 power, but require more upkeep and effort to use in the field.

Projectiles.
There ade very few guys who elaborate on projectiles with their project, most of the time its understood that you will be shooting vegatables. For our purposes i figured id share a few options more suited to airsoft.
Milsimlabs.com has foam "moartar rounds" which should be more than adequate for indirect fire, although i doubt their use as a rocket simulaid. I have found that the best round so far is a pvc rocket round built by spudtech forums in which you heat and flare one end to fit tightly in your barrel, and cap the other end with a tennisball. The generaly accepted nerf pocket vortex, by all accounts is only marginal in performance due to its light weight. There is not enough mass there to carry energy downrange. For a stable general purpose round the tennisball seems to be the answer, as its fuzzy surface reduces barrel friction and they come in 2.5" standard or 2"pet toy size.

Further work will undoubtedly take place and i will post up what i learn.

[cloakndagger]

The artillery section so far.
2 12g co2 powered 2"barrel man portable launchers, sprinkler valve trigger.

One ball valve 12g co2 2"barrel law (purchased online)

And in construction, one combustion type launcher, electricaly fired.

Info on the last build to come shortly

[cloakndagger]

Ok, just got in from the shop, here are some more bits of useful info.
Combustion air cannon, or true potato cannons.
These are super simple machines, that rely on combustion of a propellant, usualy aerosol propellants in hairspray etc. But just because there are few parts doesnt mean there isnt a big secret.. and that is........barrel to combustion chamber ratio!  This determines whether you dont have enough burn to get the potato on its way, or you waste energy because the barrel is too short. It is agreed by the experts that you should shoot for a 1.5 to1 ratio of combustion chamber volume to barrel volume. To find that volume you say pi x radius2 x length. In the case of my 4" djameter firing chamber, 3.14x(2x2)x13.5in.  This should provide optimal burn and pressure. No need to go any farther into construction, as google can produce way better results. For an ignition source i pirated a battery powered electric igniter set off an old grill, mainly because it was handy and id forgotten to get a piezo igniter at wallyland.

[cloakndagger]

Pre op genisis notes, so far construction seems to be done. 
Combustion cannon "recoilless rifle"
Best fuel so far is rave hairspray, but the buildup will eventualy foul the igniter points, so using a little light cleaner like pledge is recommended. Right gaurd or kerosene seem to burn cleanest but have less power.

Air cannon launchers.
After chasing leaks for a weekl i learned that teflon tape will not seal a co2 powered gun. You have to use loctite on the pressure components.
Co2 cartridge adapters are hard to find in ms. If anyone has one they dont want let me know please!

Ammo.
I tried a great number of ammo types, and have learned.
Nerf brand vortex rockets are far superior to other football rockets.
Stress balls are almost as good as nerf rockets, and are the preferred ammo for combustion cannons (as they tend to blow off rocket fins)
Anything can be ammo if you have a good piece of cloth wad.. even dirt.

[CREEPER™]

And it's all good until a 23 Month old little girl robs you of your ammo, huh?  See, maybe your ammo should be more "intimidating"!! Lol!

[cloakndagger]

Yesterday during proofing and tinkering i managed to blow the irrig valve on one of the co2 cannons. After modding a second valve i had trouble with fluttering, and finaly had t replace it with a ball valve in the interest of reliability and time constraints. I will look into making a correct fix later.