Not hitting the right OG

I´ve brewed several batches, but lately i havent been able to reach the right OG. Today I brewed an APA, here is the grain bill.

5 gallons
9pounds 6 oz 2-row brewers malt
13 oz caramel 60
12.3 oz munuch II

this was suposed to give me an OG of 1.055

But I ended up with 1.040

I think is one this factors. I´m gringing my grains in a old old corona mill. some time whole uncrushed grains, come through the top, it´s a small percentage but there are certainly some uncrushed grains, not even 5 %.

I´m probably sparging too fast. here is how im doing it: i use a 10 gallon igloo cooler, with cpvc on the bottom.

beersmith told me to:
add 13.68 qt of water 165° to achieve an 152° for 60 min.
then sparge with 5.85 gallons of water at 168°

after the 60 min. I drained the first wort, then added the sparge water all at once and drained it. I didnt keep time of how fast i was sparging but it was pretty fast:

could this be the issue or the mill, or both?

thanks

The mill is probably having some impact, but draining mash and sparge water quickly is probably the main problem. It usually takes me around 45 minutes from the time I start draining mash water to the time I am done sparging (and this is in a 5 gal cooler). I batch sparge in the same way you do.

Are you keeping track of your efficiency in beersmith? If beersmith is saying 75% efficency when its calculating OG but your REALLY hitting 65% with your your system your going to undershoot your OG every time.

My advice is to find a consistent process that you use everytime. Keep track in beersmith of what your real efficiency is and when you go to brew again plug in your real efficiency.

If you have a low efficiency its not the end of the world beersmith has a gravity adjuster so you will just need to add more grain to your batch. More grain is only a few bucks more on such a small scale.

If your just chasing higher efficiency for the heck of it then you need to evaluate your crush. Sparge time and speed. SLOW sparging rinses more sugars out and increases efficency. Finer crush also increases efficency (but the finer the crush the higher the chance of stuck sparge) so you have to find a happy medium.

Having a consistent crush and sparge time everytime is the key to predicting your efficiency, OG and grain bill accurately each time.

You also need to enter your equipment into beersmith....boil off and mash tun dead space.

You could also mash longer...90 minutes instead of 60 minutes.

Sounds your efficency is off. You can always improve your way of brewing the beer or counter it with additional 10-20% of you grain bill. Your combination of a poor grain crush and a fast sparge. You want to get about 1 hr for your sparge. I calibrate it out in my system right about a 1.5 gallon every 15 mins and adjust accordingly.