Are these two different species of wood???
I have two identical size pieces of 2X4 that are pressure treated and bought from the same dealer at the same time. There is quite a difference in the weight of the two...They are 40 " long and one weighs 3 lb while the other is 7.5 lb. The second piece feels pretty wet.
On closer inspection I noticed the markings are slightly different in that the second is S-P-P instead of S-P-F.
The first piece is marked:
S-GRN
469 NLGA S-P-FThe second:
S-GRN
469 NLGA S-P-P