Hmm. It is difficult to say exactly what is going on. What was your mash temperature? Did you undershoot or overshoot your temperature goal? Did you add any acid? Do you know the mash pH? It is possible the LHBS has a tight mill gap, however it is very unlikely. Perhaps you stirred too much. I think it is better to stir once in the beginning of the mash, and then leave it alone. This way, if a fine layer of proteins and starch forms on the surface of the mash, it can be lightly raked to allow improved flow through the top layer. But if this is all stirred up immediately prior to runoff, well then you have less control.
Excellent first post. Welcome to the forum. I hope this sparks some useful ideas.
Thank you, and everyone else, for your thoughtful responses! Really excited that my first post brought some replies. Lemme answer your questions 1 by 1:
1. Temp was bang-on (150F) throughout the mash, according to both my Foundry's internal thermometer and my Thermapen
2. Yes, pre-acidified with ~8ml lactic acid, but I did not break out the PH meter today, I normally only use that when I'm kettle souring.
3. Agreed re: LHBS crush, it seemed normal and I haven't had trouble with mostly barley grain bills that went through the same mill. Could've been adjusted I suppose, I'll talk to the employees next time I'm there.
4. Interesting technique with the mash stirring, I definitely stirred the s*** out of it nearly constantly in the hopes of unsticking it, I'll try your way next time.
I did end up using a brew bag, which worked great. I intend to do so for future wheat beers as well.
@majorservices, Ah gotcha! yes, conversion was fine, but the grain soaked up a lot of my water volume and no matter how much I squeezed the bag, I couldn't get to my target pre-boil volume. So, without thinking, I just topped off my kettle with more RO water, which tanked my OG by like 15 points.
Have not heard of a beta-glucan rest before, I'll look into it.
Thanks again, friends!