Stuck drums happen regularly on cars and is one of those real curssed type things! When it does, the word easy is not one that comes quickly to mind in relation to it. Frequently by the time your done, other words will. Make sure you back off the adjusting star all the way - even releasing hydraulic bleeder can help. Bang, bang, bang. Liquid Wrench (especially if the studs are through the drum). Various pullers (there are some common ones that can fit many wheels). This is not a time for restraint...fact is drums are cheap and may not be able to be turned (warped, worn, rusted, etc) anyway.