Grain Freshness & It's Effect on Efficiency?

Brew in progress. First time I have ever totally MISSED gravity....and by missed I mean.....MISSED.....

Supposed to hit 1.041 pre-boil gravity, came in at 1.018, volume spot on 6.7 gallons. Yikes. The only thing I changed with this one is my water/grain ratio. I was 3.5 gallons per 10.25 lbs of grain. So 1.35 qts/pound. Mashed at 153 for 90 minutes too...I used 3.9 gallons of a "pour through" sparge after pulling the bag. Same process I've been using for the last 6 months. Never missed by more than 1-3 points.

Here's the kicker. I bought the grains in October and they were milled then. Since then they have been sitting in my pantry in a sealed plastic bag that they came in from AHS.

I can go into more details about my process if needed, but I brewed with grains that I purchased at the same time (October) just about a month ago and nailed the gravity and volume spot on in that brew. BrunWater calculated my mash pH at 5.4, so I should have been somewhere in the range.

Anyone able to provide insight as to whether it might have been my mash thickness or perhaps the "freshness" of the grains?

So I've thought about this as well and when I bought a recipe I knew I wouldn't brew right away, I opted not to have the grains crushed. My assumption was there could be a loss of efficiency but I have no solid proof.

I had bookmarked this:
http://homebrew.stackexchange.com/questions/3360/effects-of-grain-freshness-on-brew-house-efficiency

I cannot imagine that your water to grain ratio caused the issues because it sounds like that is what you always use.

Thanks for the link. I'll check that out. I admit, there are a LOT of variables here...pH, thickness, freshness, mineral additions, etc... I don't have a way to accurately measure that, so I'm going with what BrunWater says it will be and I adjust my mash thickness to keep it in the range. For instance, my IPA that I brewed last month that I hit spot on was mashed at 1.7 quarts/pound because that made the pH calculate at 5.3. I KNOW this isn't the best method, but it has worked for about 4 brews now.

I bought the AHS Weekend Warrior package (4 recipe kits for $100 and free shipping) when they ran that deal back in October and I've only brewed 2 of the 4, 3rd one today. I'm thinking that maybe I need to invest in a grain mill and stop having them mill my grains.

Ok I think I'm losing my mind....I either really really screwed up the pre-boil reading of the gravity, or I magically made up the gravity points I was missing. I just finished my boil and chilled a sample and it came to 1.051 which is what my recipe says it was supposed to be....

Now I am really.....really confused haha. Good news I suppose, but how do I screw up a reading THAT bad? The sample was at 72F (68 is ideal I know, but close enough not to make a 20 point difference).

And I haven't even had a beer yet today!!

I think I figured out why I gooned up the initial pre-boil gravity reading! I do BIAB and use "pour through the grains into the BK" method to sparge. What I forgot to do was stir the BK before taking a sample. This resulted in the "sparge water" being on top where I pulled the sample from. Had I fully mixed the wort+sparge in the BK first, I probably would have had a more appropriate OG reading. Hopefully my confusion and mistake will help someone else!

In other news, the AHS grains that came in the thick sealed plastic bag seem to have maintained their "freshness" for at least 3 months at this point. I have a stout to brew in a few weeks using grains purchased at the same time. We'll see if the efficiency suffers with that brew.