In my humble opinion, most opinions are wrong. the bolt is about repeatability and consistency.The boltputs even pressure on the cartridge, and is consistent round after round, as the lockup is right behind thebrass. Where a lever, lockup is before the bolt. Where a breakopen,can have inconsistent pressure behind the brass due to its lockup is not even.

The bolt also can have consistent pressure on the barrel,or consistentno pressure on the barrel,where the lever, pump, or break open you cannot.