I have the "Barley Crusher" as mentioned above. It's okay. Yes, it crushes grains. But it also gets jammed occasionally, isn't gear driven (the second roller just free spins) and sometimes just seems to skip through the grains. This is probably due to the free spinning second roller and the fact that mine (and other club members' BC) doesn't seem to want to stay at the gap setting I put it at. Five or so batches and it needs to be put back into place.
I have the same Barley Crusher. I recently noticed a dip in my efficiency on my past couple of batches. I had attributed it from switching from a hand crank to a drill, but now I'm wondering if it is simply because of the mill gap loosening up. I'll have to check it out tonight.
Do finitely check the gap setting periodically but also be sure you are using a variable speed drill and set it to go as slow as you can.
When I first used a drill I found a dip also and it turned out I was milling too fast.
I've always set me drill in highest speed, and locked it so I didn't have to stand there. But after reading your post, I tried the last batch of my Amber while milling the grain at about half speed.
No difference in OG. I brew this same beer once or twice a week, and I nail 1.060 exactly every time. And this time as well. All water volumes and mash temperature were the same.
I'm going back to high speed milling.