I thought Whippets were nitrous oxide, not carbon dioxide. Am I imagining this?
Sorry.
. Continue.
Yeah, that's the colloquial term for the NO2 carts.
CO2 comes packaged in much the same way, in steel pierce-pin cartridges. They have 8, 12 and 18 gram (by weight, of course) carts and some other sizes that are less common. Because they vary by size, you need the correct-sized adapter for the cart size you want to use.
Also, 12g carts are very common for use in air guns and air-powered portable tools. To manufacture them, they are pressed out of sheet steel by a set of dies into long tubes and then crimped into cylinders. A significant ammount of lubrication is required in the pressing process and some of this stays inside the cart when it is filled. It's just air tool oil so it's actually beneficial to the tools and guns they're used in but it tastes
nasty and will destroy your head if used to carb or press beer with. You need to get food-grade carts which are scrubbed after forming, contain no oil and are about 3x as expensive. You can't just go to WalMart and pick up a 20-pack of 12g carts.
I've used 12g carts in a pinch trying to dispense at the after-paintball party. It works, but the results are less than stellar. In the middle of the woods, few people mind but it's not something I'd do on a regular basis.
Honestly, aside from the added cleaning workload, bottles aren't that much more work than kegs. I used bottles exclusively before jumping up to kegs (though I did use a few growlers -and one champagne bottle- here and there when I had them). I'd recommend bypassing the middle stuff altogether.
Both bottles and kegs have their advantages and disadvantages. I still use both depending upon what I need to do with them.