Have you considered that your issue may be too much water?:cross:
I'm suspect of his mash calculator because I ran his recipe through BeerSmith and got way different strike and sparge volumes. I'm not saying that crush isn't a contributing factor, but too much water = low OG.
I definitely agree with you. If you use too much water than your preboil and OG will be low. And if you use too little water your preboil and OG will be higher.
What I was trying to say was if a brewing software was used, I highly doubt the low efficiency was because of too much water. The brewing software will calculate how much water based on grain and equipment (boil off and tun dead space).
As long as the recipe OG and brewing software OG match then the user should get the estimated preboil. Now if the user entered something in wrong and the brewing software OG was lower than the recipe OG, that would cause a problem.