Well
Not uncommon for Flat Sawn 6" wide RO to shrink 1/2 in width after dry...
Check woodweb's calc
http://www.woodweb.com/cgi-bin/calculators/calc.pl?calculator=shrinkage
The amount of shrinkage calculated is:
0.5811 inches
or:
0 19/32 inches
(rounded to nearest 1/32 inch)
The information you entered was:
Width: 6 inches
Initial Moisture Content: 0.3 (decimal percentage value)
Final Moisture Content: 0.06 (decimal percentage value)
The type of lumber you chose was: Flat Sawn
The Shrinkage Percentage Value used for
the species you chose (Oak, Southern Red) was: 11.3%
Also Check NHLA rule #4 (near the begining of the rule book) also Check rule 2.12.4.1 (the end of the rule book)