I crush at the Homebrew Shop where I get my grain. Full volume is likely. I do know from my last batch I lost a ton of water to the grain bag so went on the high side. 60 minute boil is my current plan. But that might change.
Don't be afraid to squeeze the bag and get all that great wort out. Squeeze as much as you need to hit your "Pre boil volume".
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The volume numbers I have settled on have come from jotting down what happens during every brew. Eventually, once I got my crush where I wanted, all the numbers kind of fell in line and became easily repeatable.
Here's a recent beer I brewed and how it all adds up:
Goal is to fill my 2.5gallon keg.
6.5 # Grain for a 1.047 OG beer
Grain absorption = .11 gallons/lb
Boil Off Rate - .67 gallons/hour
Kettle Loss - .625 gallons
Fermenter Loss - .5 gallon
Count backwards...
2.5 gallons packaged
+ .5 gallon Fermenter Loss (yeast, hops, whatever that gets left in the fermenter)
+ .625 gallon Kettle Loss (gunk that gets left behind in the kettle during transfer to fermenter, a completely fungible number)
+ .67 gallon boil off (assuming a lazy, 1 hour boil)
+ .715 gallon grain absorption
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Total Mash water = 5.01 gallons or 5 gallons for homebrewing purposes.
Grain absorption is going to be greatly influenced by exactly how long and how hard you decide to squeeze the bag after mashing. I squeeze only enough to hit my "Pre-Boil" volume and stop there. My "Pre-Boil" volume is ALWAYS 4.3 gallons (2.5 + .5 + .625 + .67).
Which leads to another point if you are using a standard kettle: Try and find a reliable way to measure your kettle volumes. There are a lot of ways to do this, but I ended up filling my kettle to different levels and measuring with a stainless steel ruler. So as an example, my typical strike volume of 5 gallons in my kettle = 7-1/4" on the ruler. My "Pre-Boil" volume (the volume to which I squeeze the bag) of 4.3 gallons = 6-1/4".
Hope this helps. Good luck.