Originally Posted by bigben
So you're saying that even if you left out the grains your OG wouldn't be .02 off? What the heck could it be then???!!!
With 3 pounds of grain and like 5-6 pounds of extract, the grains are contributing less than 40% of the OG, so yeah, even if I left them completely out, I'd still be at more than 60% of my target OG.
Since you are using more grain and less extract than I do, your mashing does have more of an effect on your OG. Did you take any measurements of the specific gravity of the wort you got from mashing (prior to adding any extract)?
Unless you forgot to add a couple of pounds of extract or something, it seems like you need to check typical mash problems. I'm no expert here, but I'd suggest: making sure your grain is properly crushed, using a good mash schedule (temperatures and water volumes), making sure the mash is thoroughly mixed, etc.
It's probably not a bad idea to take a SG reading of the wort that you get from the mash, to make sure you're actually extracting something, and I also like to do the iodine test to see if the mashing process actually worked (starch converted to sugar). Tasting that wort is also a simple sanity check - it should be sweet, and not too watery.
I've got a little documentation of my first partial mash, which may give you something to compare to:http://eegeek.net/content/view/72/39/
The wort I collected after the mash was 1.076 SG and after sparge was 1.068, tasted sweet, and showed no starches with the iodine test