I have several friends that shoot in high level matches like the trials for Friendship IN, the Olympic trials in CO, etc. (2 of these guys have been to and came home from the Olympics with one gold and several bronze metals a few years ago).
That said I have always paid attention to what they shot, type of ignition, barrels, twists and breech arrangements. A correctly fitted hook breech is as good as a fixed breech and in many cases better. Consider this, a hook breech is finely tuned metal parts matching with each other while a fixed breech is metal mounted against wood. Over a short time the wood metal fit will change while the metal to metal will change after years of service, but not as bad as the other.
A good example is if you get a chance to go to serious State Championships or National level matches look at what is winning year after year. If any of you remember the name Ron Long of "Long's Locks" - he's of an Olympic Gold Winner that shoots both style breeches depending on the match, distance, etc. Ron is a perfectionist at his craft as well as his shooting routine, he is a shooters dream in how he prepares and executes each shot. Its not very often you see a good shooter have perfect days or weekends with every target shot having scored 49-50 (5 X's).
Practice and paying attention to the breech plug fit, barrel keys or pins, ball weight (all within 2 grams of each other), patch thickness and weave of material and so on are all part of the game these professionals go through at each match.
NRA/NMLRA Life Member
Basic Rifle, Pistol, Shotgun
Basic Muzzleloading Rifle, Pistol, Shotgun