This question assumes you carry a secondary/BUG, and train to transition to it if your primary stops running for any reason.
Since you will transition to your secondary/BUG, does it make any sense to carry a reload for your primary? If you carry a reload at all, wouldn't it make more sense to carry reload(s) for your secondary?
I suppose you could imagine a scenario where you run your primary dry, but cannot get to your BUG...but in that case, you probably cannot get to your reload either.
With a limit to all the stuff you can carry, I'm just wondering what those of you who carry a BUG do for reloads?