Michael Ray Forehand in his book "Advanced Competition Shotgunning" wrote that the "Live Bird" traps are 31 yards from the shooter. When the bird is released "if" the shooter is fast he will get his first shot at the bird six feet from the trap. That would be 33 yards. If he misses the second shot would most likely be around 40 yards.
I highly recommend this book to any serious Helice / Pigeon shooter.

Mike Proctor