google can tell you the official distance any networking cable (cat5, cat5e, cat6) can go for footage.
In reality? Further. How much further? Now comes the realm of what if's...
how good is your copper in that cable? cheezy or professional grade?
any kinks, tights turns, nearby electrical, 3phase, any cables under pressure (torque, stepped on, twisted, etc)
I've never ran 320'+ of cat6 for video, just computers and AP's. Max was around 430' and wireless AP's still did their job for the intended purpose (those dinky bar code scanners).
Keep in mind that the 100 meter spec dates back to the days of ethernet on coax and was developed due to round trip delay times on coax. It was then applied to 10BaseT for the same reasons. Given that the normal network speed in use today is 100 megabits the round trip delay has been reduced by a factor of, roughly, 10. Now the governing factor is how far PoE will work based on the DC resistance, power loss, of the cable. In reality I pushed 10BaseT to almost 400 feet without a problem, but that didn't use PoE which didn't exist back then. I'd guess 350-400 feet should be workable with a simple camera with built-in IR lighting, call it a 10 watt load worst case. For a PTZ, all bets are off past 100 meters, ~328 feet. Remember that 100 meters includes any patch cables as well and should allow for a fudge factor dues to extra connections if using a patch panel.
