My thought is to handload subsonic 300blk out rounds with 208gr Hornady Amax or 220gr Sierra matchking and SBR this rifle (Remington 700 Tactical SPS) down to about 10.5 inches (efile for tax stamp) and direct thread my AAC Cyclone suppressor on the end. (after I drop in a new trigger).

http://www.budsgunshop.com/catalog/product_info.php/products_id/80179/Remington+700+TACT+300+BLK+OUT

Thoughts? Other options to get the same result? I'm trying to get to a highly accurate bolt gun for taking out hogs with headshots as quietly as possible at about 65 yards.

Is this ideal in terms of bullet stabilization, etc?

I'd keep it the 16.5", but if you want to go through the SBR, it would work. I'd recommend an AR-15 platform for the SBR, since you can register the lower and have multiple SBR uppers.

I have 2 Rem bolt guns in 300 blk out, and they do fine for hunting. But I use my supers for hunting, not subs. Your 208 A-max and 220 SMK will not expand. Shot placement needs to be head, neck, and spine for effective subsonic hunting. A shoulder shot will allow the animal to run, often a good ways.