I've always tied nail knots, even going to the extent of learning the nailess nail knot so I could tie one without a tool of any kind. I've always like the nail knot as a direct connection for the butt of the leader when using long leaders for the best transfer of energy. I just learned the Castwell knot from this post, tied a small perfection loop in a leader butt of a 15' leader and tried it. No discernible difference in turnover. I also couldn't break it. Just amazing. You can adjust the knot before tightening to lose almost nothing off the end. I then tried it on a piece of T-14 shooting head. Unbreakable. Just made it incredibly easier to put sections of sinking line mid-leader, as I like to do for steelhead. The only thing I could see was the connection to the end of the shooting head made an abrupt 90 degree face that could hang up coming in the tip top. A drop of Aqua Seal or Knot Sense would cure that very quickly. This is the best tip I've learned in ages. Thanks Guys!!!!!!!
Charlie