Since it's a barn (to start), why not all green SYP dimensional lumber ??

[Sedgehammer]

They will cut it however I want, so as was mentioned earlier in another thread, one can get pretty close to kiln dried by adding a little bit

Down side is can't build a 27' tall wall with a single stick, like can with DF

A 2x8x16' SYP RC is $16, so wood be a lil-bit cheaper if 1-5/8 x 7-5/8 (or what was good for SYP). A 12' 2x8 is $12, so a 2' OC full length is about $32 vs $88.

Any down side besides single stick wall?

The walls wood be more than 50% cheaper

[woodroe]

Depends on what you use for siding.
If you were to use green board siding it would probably all
shrink together. If you were to use metal siding or plywood/chipboard sheathing  
you will end up with gaps at the shoe and top plate when the studs get done shrinking.  
Unless you buy roof trusses, same scenario with roof framing.
Other than that, you could frame it all up and let it air dry some .

[Nebraska]

In very short order that pine  once put up would be as dry as the kiln dried stuff you bring home from the box stores anyway.  Might be some fastener issues as far as shrinkage.  Lots of barns have been built with green wood.

[Sedgehammer]

I'm going to go through the plan and get a material list and check prices. I also need to figure shipping, as it will be a semi load. 

[Sedgehammer]

2x6 16' OC has 2.9 inches of wall it supports

2x8 24" OC has 3.2" inches of wall it supports

If you multiply the thickness by the width a 2x6 is 1.94

a full 2" x8 is 1.6, so it's stronger. A 2x8 (1.5x7.25) is 2.2

That's not a lot of difference , but it's a difference. I could cut the wall 2x8s a full 2' thick to make up that difference or you think 2x6 16" OC is better over all?

If 2' OC studs, sheetrock for the walls wood need to be 5/8?

I'll do 7/16 on the exterior walls, as I need to run a 1x3 or 1x4 to screw the B & B to, so that should be enough for shear strength.