Chris,
If this is your first encounter smoking butts in the Bradley and you're going to do 30+ pounds, I would seriously consider preheating the smoker to at least 260-280, put the butts in, smoke for 4 hours and then move them straight to your house oven to complete. 30+ pounds of meat in the smoker will really take a long time for the heat to build back up in the smoker. Butts are very forgiving but if this is your first time and you're cooking for family and friends you want all the help you can get. One thing to watch for if you do move to the house oven, does your oven have a built in timer that will only let your oven run for so many hours and then shut itself off as a safety feature? Mine does I found out the hard way. If it does you may have to start your oven more than once but that's no big deal. One other thing, when you put those butts in your smoker, make sure they are not touching the walls or the back. Don't want the grease running down and starting a grease fire in the Bradley of yours!
Good luck and let us know how it goes!
KyNola