Re: Fire Formed Brass?
Try and chamber the brass you have now. If it will chamber, neck size and go shoot some starting loads.
Once the brass has been fireformed in your chamber, neck size and work up load for that rifle.
Once fired brass comes in a variety of sizes depending on the chamber it was shot in. If the brass will not chamber in your gun, you will need to FL resize then shoot some med. loads. Neck size from that point on. Watch for case head separation - will show up as a bright ring just ahead of the belt.