Yield question?

I seem to be only getting 4.5 gallons out of a 5 gallon batch. At first i thought it was loss from transferring from primary to secondary to bottling bucket, but my last batch I kept in the primary until bottling day. Still only managed 48 12oz bottles, and the last one I had to really work to fill. Maybe only a good 47 bottles, the 48th was finished by pilling the wand and getting every last drop in. I always expected 53-54 bottles from a 5gal batch, but that hasn't been the case, any advice would be appreciated.

A lot of liquid gets absorbed/caught up in the trub at the bottom of the fermenter. Try transferring 5.5 from your BK into your fermenter next time.

I know in 'Brewing Classic Styles' they write recipes that are 7 gallon boils. Assuming you have 6 gallons left after the boil, transfer 5.5 to the fermenter and bottle/keg 5 gallons. So, they figure on you losing about 1 gallon to break material and trub.