Originally Posted by kaboom133
I regularly mash at 1 qt per lb with 75% to 80% efficiency. At 77% with 21 lbs of 2-row its 5.25 gallons and about 1.210 O.G.
Recheck your math.
I believe you're looking at about 1.114 with 21lbs @77% for 5.25 gal.
For 1.210 you'd need 38.7lbs of 2-row @77%.
...and as has been mentioned you're not going to get 77% for gravity that high (unless you sparge half the day and boil for the other half).
For me it's somewhere between 1.090 and 1.100 that my efficiency starts taking a noticeable hit. At 1.100 I'm probably around 4-5 points lower than my normal efficiency and it gets worse the higher I go. I could continue sparging to rinse out all of the sugar that's being left behind but then I'd be looking at a 3-4 hour boil to get down to volume. No thanks.