Related question here...as @radagast said above, extract brews are "difficult to get a true gravity reading on because of the near impossibility to get a completely uniform mix".
I just brewed my first 'scratch' extract recipe - which means there are no instructions or recipe to tell me the expected original gravity. I usually take a hydrometer reading before pitching my yeast and only once in all of my 11 brews over the past 6 months have I even gotten even close to the expected gravity (i got within .002).
Last night's brew gave me an OG of 1.038 and I'm confident that is low. Anyway to determine an expected OG from the ingredients.
* Pre-boil 3 gallons of water
* Steeped 1lb of Weyermann Cara Amber Malt grains at 150* for 20 min
* 6.6 lbs of Briess Pilsen Light LME
* 2 oz of SAAZ pellet hops @ 60 min
* 2 oz Mount Hood pellet hops @ 20 min
* 1 oz Hallertau Mittelfruh pellet hops@ 5 min
* Cooled the wort and topped the volume to 5.125 gallons @ about 75*
* Took a sample and hydrometer read 1.038 (I would have expected something about .008 - .014 higher)
* Pitched the us-05 yeast
* Currently sitting in fermentation chamber @ 64*