I have been reloading .223 rem for the last few years and finally got a bolt action .308 win. I am loading the first rounds now and I am a bit concerned with potential over pressure.

Issue #1
I have factory new Lapua brass and CCI #200 and IMR 4064. The problem I think is the Barnes 165gr TSX slug. Since its solid copper its longer than its lead cousin, and seats deeper into the neck. With the min charge there is no air left in the case, so as soon as I go above the min charge I will be running compressed loads. Is this safe?

Issue #2
I do not have the actual Barnes #4 Reloading manual, but someone posted it on another forum. It shows 42.0gr start and 46.0gr max. Is this correct for Barnes 165gr TSX and IMR 4064? I am going to stop by my local Cabelas tomorrow to get the manual.

Imr 4064 is one of 'the' 308 win powders. I have researched it a great deal. I do not load Barnes, but 42-46g is pretty standard for bolt guns w/ other big name bullets.
Start at 40g and work up in .5g increments looking for pressure signs.
You can get Nosler and Hodgdon info on line. Hodgdon now owns Imr, so Imr powders are listed on the site. 6mmbr.Com also has 308 Win load data.
Hope this helps

I shoot 165-168 TTSX outta my 308 Scar, either 42.5 grains TAC or 40 grains 8208; get the same preformance; I like both those powders over 4064. We have killed a few caribou & a grizzly bear with those loads last August. I seat mine so they just fit in the mag, which is about max most books recommend.

I shoot compressed loads all the time. As long as the bullets don't push out of the case you're fine.