Lead vs Bismuth in reloading

[Matt Valinsky]

I have not used Bismuth for reloading and have no knowledge of the beast, so the reason for my question.

I have found a 16ga. recipe which I have all required components, Cheddite hulls, cheddite primers, SG16 wads and Green Dot powder. In this particular recipe the playload is 7/8oz. of Bismuth which I don't want to reload, I would rather use 7/8oz. of lead. I have read that all things being equal that 7/8oz. of lead will generate lower pressures than 7/8oz. of Bismuth. from what I understand it's a volume thing.

So, my question to the folks who know the answer, is this true?

In the Bismuth recipe with 15.5 grains of Green Dot the average velocity is 1221 fps and average pressure is 5803 psi., this is a tested recipe.

Thanks in advance.