New guy. 1st recipe

[scmurray]

Yeah, so assuming the same batch size and lauter/sparge strategy, you can expect a lower mash efficiency with the bigger beer. How much difference to expect depends on your particular setup, but I just ran some numbers (yours, more or less) through BrewCipher's Mash Efficiency Predictor. With my setup, and with single batch sparge (and a couple of other assumptions), it predicts 70% mash efficiency to drop to ~65.5% with the larger grain bill. That alone would explain over half of your mash efficiency drop.

Thanks for the explanation