That's a good question. I will admit that the coolness factor of a 100rd drum overrode the thought of practicality.
Some quick online window shopping shows the shipping weight of 100rd 9mm (Hornady Zombie-Max) as 3.124 lbs. A Glock 17 (unloaded) weight is 22.22 oz. Not counting the mag, which I couldn't find the weight for, we're at just over 4.5 lbs. So, fully loaded with 100rds would probably be around 5 lbs vs 2 lbs for a loaded Glock with 17rds. Heavy, but not really unbearable.
I'll just keep it simple with this:
Attachment 1769 Although I wouldn't buy that now since I don't want to go through all the ATF red-tape to legally use one of those.