Why Straight Rifling?

Christian Oerter Letter
18th-C Apprenticeships
Curly Wood
Fantasy Rifle?
Scratch Built???
Iron & Steel
Muzzle Blasts
Hunting Stories
What's a Virginia Rifle?
Why Straight Rifling
Originally posted in response to a query on a message board.
Archers had used spiral fletching on arrows for centuries before firearms were invented. They may not have understood the physics involved but the arrow makers learned early on that selecting all the feathers from the same wing and gluing them at an angle imparted a spin that improved accuracy. There were even some crossbows that shot a bolt with no fletching that got its spin by being oval in cross section, being twisted and being fired through a tight fitting aperture in a plate at the “muzzle” of the crossbow.

In answer to the earlier question about why bother with straight rifling—In a smooth bore WITH A LOOSE FITTING BALL you can shoot either a knuckle ball or a curve ball. A curve ball happens when random drag between one side of the ball and the barrel (at the muzzle) imparts a spin across the axis of the balls travel. This spin generates different pressure on the sides of the ball and causes it to curve just like the deliberate curve a pitcher can throw. Problem with the curve on a musket ball is it can break up, down, right or left and to different degrees between shots.

A tightly patched round ball in a smooth bore is unlikely to become a curve ball but a patched ball in a straight rifled barrel can never become a curve ball. It is a knuckle ball and has that amount of variation in flight so it is not as accurate a spiral rifling but it is more accurate than no rifling and has the added flexibility be being used to fire shot without disrupting the pattern the way spiral rifling does.