With regard to holding back, I doubt it. I am moderately familiar with the international BP/muzzleloading fraternity, having participated in competitions in England, France
, Germany
, Italy
and Austria
, and find that people are quite willing to discuss how and why they do what. The behaviour of minié-style (hollow-base) bullets has been studied intensively for more than a century. I am also one of the relatively few contributors to use my own name, and am correspondingly unimpressed by hints of secret knowledge possessed by anonymous persons who cannot produce a single competition result to back up their opinions.
If I am wrong, let's have names and facts!