What’s the difference between fixed-blade and mechanical broadheads?

The bench has considered this question at length, and the Codex is unambiguous. A fixed-blade broadhead carries blades that are permanently open, rigid, and in their cutting position from the moment the head is assembled. A mechanical broadhead — called by some an 'expandable' — carries blades folded against the ferrule during flight, deploying outward on impact through a cam, pivot, or band mechanism. These are the two lineages, and they differ in ways a serious archer must understand before spending money or drawing blood.

Fixed blades are aerodynamically demanding and unforgiving. Their open blades interact with the airstream, and any imbalance — a bent blade, an off-center grind, an arrow that is not tuned — will reveal itself in flight as a radical departure from your field-point impact point. This is not a flaw in the head; it is the head honestly reporting the state of your bow and arrow system. Fixed blades require a well-tuned bow, correct arrow spine, and a point weight matched to your setup. In exchange, they offer no moving parts to fail, no minimum impact velocity to deploy, and a penetration profile that depends only on blade sharpness and arrow momentum. Blade widths typically run 1 inch to 1.5 inches cutting diameter; weights commonly 100 or 125 grains.

Mechanical heads fly more like field points because the blades are tucked away, reducing drag and lessening the penalty for imperfect tune. Their deployed cutting diameter is often larger — 1.5 to 2 inches or more — which is part of their appeal. However, they require a minimum impact velocity, typically somewhere above 220 to 250 feet per second depending on the design, to deploy reliably. They also surrender a portion of the arrow's kinetic energy to the opening mechanism itself, which reduces effective penetration compared to a fixed-blade head at equivalent momentum. At sufficient speed and for appropriate game this is rarely decisive; at marginal velocity or on heavy-boned animals it can matter considerably.

For a newcomer whose bow is not yet precisely tuned, or whose arrow spine selection is approximate, a mechanical head may group better and build confidence. For a hunter whose arrow is tuned, whose spine is correct, whose draw weight delivers adequate kinetic energy — typically a minimum of 40 foot-pounds for deer-sized game, more for larger animals — the fixed blade asks nothing more than a sharp edge. The Committee, naturally, has no public position on any of this, which the Guild finds characteristically convenient.