Complex sentence: The barrel is then placed slowly rotating rails so that a round barrel will rotate at about\\ frac (where Din is the inside barrel diameter in inches) RPMs or a hexagon barrel will rotate at about\\ frac RPMs Raymond Rodebaugh/Alan Silverstein.
Split into simpler sentences: The barrel is then placed upon slowly rotating rails so that it rotates-if round-at about\\ frac (where Din is the inside barrel diameter in inches) RPM. A hexagonal barrel will rotate at about\\ frac RPM Raymond Rodebaugh/Alan Silverstein.