I never can seem to draw new bows fully either...it helps (for me at least) to have something like tape on the arrow so I feel it at the correct draw length, then practice drawing it with my eyes closed and feeling what it is like to get to full draw. You know it will make it to 27 in one part of your brain, but another part is probably waiting for an explosion! Once you have done that for a while, it should be easier.