Which choke has the most open pattern?

The cylinder bore choke has the most open pattern among the options provided. This means that when a shotgun with a cylinder bore choke is fired, the shot spreads out more widely as it leaves the barrel. This is advantageous for shooting at closer ranges, where a wider shot pattern increases the likelihood of hitting a target.

The cylinder bore is essentially an unrestricted choke, allowing the shot to exit the barrel without any constriction. This maximizes the dispersion of the pellets, making it easier to hit moving targets or when engaging multiple targets in a short time frame.

Other chokes, like full choke, modified choke, and improved cylinder, have progressively tighter constrictions that result in narrower shot patterns. This tightness helps at longer ranges for greater accuracy but is less effective for close-range shooting, where an open pattern is desirable. Thus, in the context of achieving the most open pattern, the cylinder bore choke is the correct answer.