I did an experiment today I filled one of my cobs with baccy then emptied it and filled the other cob with the same baccy. I found that both cobs hold about the same amount of baccy. Wow big experiment you might think but one cob (legend) smokes faster than the other (diplomat).
Is this normal for pipes?
cob-pipes by Dai7261, on Flickr
Smoking Times - different bowls, different times?
A rough guess, surface area to coal. A wider area burning would burn quicker if your puffing was at the exact same tempo and strength. It is a reason why some pipes with narrower chamber diameters are better for flake and plug as they burn slower and plug and flake are traditionally stronger and more intense.
in goes your eye out