The AR2078 and adding a bottle to in the future would involve cutting out or up the stock- but the adapter block needed is available: http://scopesandammo.com/storefront/...nk-block-p-831

If carving the stock is not your thing, the only other way to bulk fill it with Co2 is an adapter like this: http://scopesandammo.com/storefront/...nk-block-p-831

Or, if the idea is to use HPA, then an HPA tube kit (coming back again soon) would need to be used.

If all you really want to do is plug&play a 9oz Co2 bottle or 13ci HPA bottle, the easiest and cheapest method is to just purchase the AR2079 to start.

The weight difference between an AR2078 in unmodified form and the AR2079 is a couple pounds when a full 9oz bottle of Co2 is attached.