Bullet seating with a lee hand loader?

Hello all I am new to reloading and pick up a lee hand loader for my Rem 700 ADL 270 win . I am having a hard time with the seating of the bullet the paper work that comes with the kit tells me that the COL for a 270 win is 3.340 and the max trim is 2.540 ... Can i take a factory round to set up the seating depth and still use a bullet from a different maker like hornady and use a powder charge from data form the powder i well be using ... any help is greatly appreciated