Mechanical broadheads were developed to solve the problem of poor arrow flight and problematic tuning when shooting arrows tipped with fixed blade broadheads. The solution: the blades are tucked neatly into the head during fight, producing less surface area to cause problems with arrow flight.
When mechanical heads first came on the scene, horror stories abounded. Early adopters told cautionary tales of blades failing to open or simply breaking on impact. Today, those initial problems have been largely solved by technical innovations, and mechanical heads are now widely considered a good option.
There are two primary advantages to mechanical broadheads:
Accuracy - The main reason mechanical heads have increased in popularity is the fact that they allow you to maintain the same degree of accuracy when switching from field points to broadheads. Because they are closed during flight, they fly as close to the way a field point flies as possible. About 90% of the time, the point of impact will stay the same and you won't have to worry as much about the perfect tuning of your bow.
Cutting Diameter - Mechanical heads also have the added bonus of producing more trauma, primarily due to the larger cutting diameter of the blades. This can result in a faster kill and a more easily followed bloodtrail.
Although the advantages to mechanical broadheads are undeniable, like most things in bowhunting, there are trade offs. The main drawbacks are:
Penetration - Because mechanical heads burn some of their energy in the process of opening the blades during impact, they may not penetrate as well as fixed blade heads. They are more likely to break or change direction on impact with bone, causing less-than-lethal shots when the arrow hits outside the ideal kill zone. They may also have a higher probability of deflecting when shooting at a quartering animal.
Durability - Because they're not as simple and rugged as fixed blade heads, mechanical heads require a bit more care during field use. They're not exactly fragile, but they do have more parts and therefore more that can go wrong if not protected from undue abuse.
Failure - Although the design and manufacturing quality of mechanical heads is at an all-time high, the possibility still exists that a mechanical head will outright fail. It's possible for the blades to open early, open late, or not open at all â€“ none of these situations are desirable for you bowhunt. However small it may be, that possibility, is still there. In contrast, with fixed blade heads, that possibility is essentially nonexistent.
Price - Mechanical heads can be much more expensive than fixed blade heads. Again, you should strive not to let price be the determining factor in your broadhead decision. However, it certainly may end up playing a role.