LaEscopeta, the speed of sound around sea level is about 1,100 ft/sec. It has taken a lot of experimentation to make a bullet that will expand even a little bit when driven below around 1,300 ft/sec or thereabouts. That's why handguns, with their velocity ranges around 700 to 1,400 ft/sec, are marginal for hunting when compared to rifles.
Generally, bullets are a large bundle of compromises, and there is a lot of variation in the construction for the various uses.
A target bullet need not expand at all. A bullet intended for large game has a design which gives penetration as a primary feature. Varmint bullets, intended for little critters, are designed to dramatically come apart upon impact--and some are so lightly jacketed that they spin apart upon leaving the muzzle.
Art