It has been done in paintball where CF barrels have been given an internal ceramic coating which gives better lubricity between gelatin and barrel, but in paintball there's no material slicker than brass with stainless steel and hard nickle coated brass as close seconds. The problem with brass is that it's soft, heavy, and requires more care than stainless. Stainless itself is quite heavy and that's why aluminum and CF came into the market to save weight at the cost of "slipperiness" of the barrel, they're also cheaper to produce since the tooling for stainless is pretty expensive and brass is probably the cheapest material to work in terms of tooling and maybe even raw material cost.
In all honesty I don't see CF as a barrel material in airsoft for several reasons. The first being that you can't see the inner barrel and part of the allure of having CF is showing it off. Beyond that I agree that it doesn't make much sense to use CF to save weight given the nominal weights of inner barrels already combined with the outer barrels which are made of materials which have there own heft to them. I'm not so concerned about the barrel being damaged by a nozzle since there are ways around that, including having an aluminum or steel hop-up chamber section integrated into the barrel itself.
The only thing I can see using CF for, as a barrel material anyway, would be for bolt action weapons. The reasons are quite simple: First bolt action weapons are typically going to be sniper rifles which would require a stable inner barrel to see maximum effectiveness. CF has an extremely low expansion rate and would be far less effected by changes in ambient temperature than other metallic materials, this means that your 6.00mm CF tightbore would effectively
always be a 6.00mm barrel. Second is the sound deadening qualities of CF over aluminum, brass, or steel. This would make an already quiet platform even more quiet. Combine these two features of CF with a weapon which has a low ROF and minimal chances for jamming or missfeeding to damage the barrel, and I think there might actually be a market for a product like this. There's a third feature of CF which makes it attractive, though maybe not so much, is that CF exists in one of two states (typically), it's either how it was made or it's broken. CF can also take a fair amount of abuse (as demonstrated by it being used in arrow shafts) so it isn't a porcelain doll that needs to be handled with kit gloves.
I dunno, I think I'm just rambling now out of boredom. Being stuck at home with nothing to do for almost two weeks solid is harder than you'd think.
Hey Rootbeer, if you're really jonesin' for a CF bit to put on a gun, Laylax has a Carbon Fiber outer barrel and receiver kit for the VSR-10 for the low low price of $700.
