RE: Appropiate Bullet Weight
A lot of this will depend on the twist rate of your barrel. Most .270's are made to be more of a big game caliber and shoot larger bullets, which can limit their ability to launch smaller, faster bullets accurately. Unless you are planning on using the woodchuck for something, shoot whatever your rifle shoots accurately. I would experiment with different bullets and powders regardless. Shooting quarter-sized groups at 100 is one thing, but keep in mind the size of your quarry. Shooting at 350 yards means your groups are going to be 3.5x larger, which for small varmints can mean the difference between a hit and a miss.