As for the dead space in my tun is a 10 gallon rubbermade with a mesh screen tube as the filter, 2/3 a gallon is what you would calculate my dead space to be?
A lower mash temp say of high 140s will slow down my conversion correct?
I estimated your dead space from the volume you added to the tun, minus 0.12 gal/# absorption rate, and your collected volume. There seems to be about 2/3 gallons unaccounted for.
It's common for brewers to mash longer when they mash in the 140s. I've never measured the effect, but below 150 F+ you are pushing the lower limit of efficient starch gelatinization.
I'd recommend a stir right before running off the first runnings, too. When I have forgotten to do this I got reduced efficiency.It's fascinating to hear about different techniques that people use. For me, stirring before run off makes no difference.
I can only draw a correlation between lower than expected gravity on a few batches and realizing that I hadn't stirred. It wasn't a solid data set, and the effect was minor, but it seemed to be reproducible and it threw me off my usually very predictable efficiency. It's been a while, though, and it isn't really a variable in my current system, since I almost always do an alpha rest. I saw a larger effect by forgetting to stir in the sparge water. Not that I'm forgetful or anything...