Many of these high sights are this way because, the builder left the new owner material to adjust the sights to their liking, and the new owner never filed them down. Also, in the sixties, and early seventies, some older shooters remembered shooting an M1 in WWII, or Korea, and decided that a big blocky sight combination was just the thing for a muzzleloader. And, boys, and girls, thats how the sights sold as “Patridge”, or “California sights” were born. You virtually never see this style of sight on an intact antique muzzleloader.
Heat waves off the barrel is a problem, when shoots are in locations that are very hot, and or target are so close together that barrels don’t have time to cool off. But, these are event problems, not sight problems. It takes fine sights that limit excessive light around them to shoot small targets, and long range targets. When you take these two type of targets out of most shoots, you find little advantage to big square sights.
Hungry Horse