Ok so after reading this whole thread I'll pitch in my $.02. Some of it is redundant, so I apologize for piling on. I have BIAB since my first all grain brew, and my mash efficiency has balanced out around 75%. I even just did a barleywine where I hit 69%. So the problem isn't BIAB, it's something in your process.
1: Ask the LHBS to double crush your grain. It will help a ton!
2: You are using way too much water. If you're making 5 gallon batches, you should be somewhere in the neighborhood of 7.5-8 gallons, this seems like the most likely reason you are missing your gravity numbers. I have a 15 gallon pot with a 1.2 gallon/hour boil-off rate and I usually use about 7.5 gallons to start with. I end up with about 1/4 gallon of trub in my kettle, and 1/2 gallon of loss in my fermentor, so I aim for 5.5 gallons post boil.
3: as far as measuring your volume, do you own a blender with graduated markings on it? or use a 2L soda bottle, or any other container of a known size to measure your volume into the kettle. Pour in 1 gallon, Use a piece of copper pipe, and place it vertically in your kettle and make a mark on it at the water line. Then one more mark for each gallon of water you add. Take a hack saw and cut a line into the copper at each mark. Then you have a permanently marked dipstick.
4: Beersmith is worth the money, but even brewersfriend should steer you pretty well. Make sure you are putting in your ingredients and volumes accurately. These programs are garbage-in-garbage-out
5: Try a dunk back into your wort after your grains have drained. You can gain a few points of gravity that way too.
6: No offense, but it sounds like you are sort of just trying stuff without a real plan... slow down man... you have time. Be methodical, analyze your batches, try to identify the problem.
7: Follow a recipe. I don't know if you are already doing this, but it always helps to know you are making a beer that was good for someone else first.
8: Pay attention to the details. Missing your volume by 0.5 gallons can have a fairly large effect on your gravity readings.
9: Simplify as much as possible. Don't try to fiddle with every variable. It doesn't matter if your mash temp drifts from 154 to 147. People mash overnight without issues. Just ignore the temperature drift and focus on getting your initial temperature and volume correct. Keep your mineral additions basic. Try 100% RO water with only lactic acid to control mash pH. Don't try to outsmart your equipment by changing your volume drastically (1 gallon more water) between brews. Small changes, refine the process, relax, don't try too hard.
10: Mash for 90 minutes
It's always frustrating when nothing seems to be working, but that's ALWAYS because you haven't tried the right thing yet. The answer exists, you just have to work the problem and find it. Be methodical, change 1 thing at a time, stick to the recipe. Good luck!
1. This is on the list for next time.
2. I used priceless' BIAB calc to get the 9.27 strike volume figure. I estimated 1 gallon of fermenter loss, since I was brewing a NE IPA with a ton of hops, and 1 gallon kettle loss as well. I don't usually use this much, but I've been only getting about 4.5 gallons into my keg before hitting trub so I overshot this time to see what happens.
3. No, I bought a 1 gallon measuring cup off Amazon. I double checked with weighting quarts of water and it's accurate as far as I can tell. I made markings on my plastic dip stick, but I did them off lengths, not pouring a gallon each time, and it was a last minute thing. A more accurate dipstick is on the list before next time I brew, just need to figure out how to properly differentiate 1, .25, and .5 increments.
4. Been using Beersmith for every batch since the second
5. Never heard of this one. Straight back into the wort? Seems like I'd just reabsorb a ton of liquid I squeezed out.
6. Probably. I really didn't change much from my last batch to the one I brewed last night, my only major difference was switching the homebrew store I went to. I had hoped going to a dedicated LHBS with a nicer mill would fix my OG issues. Part of the problem is I have absolutely no good sense of taste - so while I can tell when I don't like the flavor of my beer, I have no clue what that flavor is or where it comes from, or even how to describe it.
7. I usually base my recipes off something, often from here, but a SMaSH wouldn't be the worst thing to do. It's pretty hard to make a bad beer with Citra and Galaxy, I feel.
8. I agree, this is why I need to figure out how to get pin-point volume measurements (although it changes with temperature, so now I'm realizing my dip stick done at room temperature won't work at wort temps...)
9. Yeah I'm not worried about mash temps, it was all within conversion range and only dropped so much since it's so damn cold in Ohio. I only used CaCl, gypsum, and lactic this time which I feel is pretty simple. I'm conflicted on going back to my tap water - on one hand, all of the beers I liked were made with it, but on the other hand I don't even like to drink it without running it through a Brita pitcher, so why would it make good beer?