I will echo what 400 nitroexpress has said -- if the bead of the front sight is too big the you limit your accuracy at distance by covering too much of your target.

The last picture with the large front bead would seem to limit the longer range accuracy of express sights.

Any pictures out there of the "best" express sights?

Could Champlin's modify/improve a Merlels express sights to a better configuration?