More often, they hinder legal gun owners while doing nothing to stop criminals from illegally owning guns. Criminals are unaffected by gun control laws because they are already trained to break the law, so they simply acquire guns illegally. Gun control laws do, however, affect legal gun owners, making gun ownership for hunting, sport shooting, collecting, and of course self-defense, inconvenient, expensive, and time-intensive. Those who oppose gun ownership can never differentiate between legal and illegal guns or between authorized gun owners and crazed killers. This leaves legal gun owners defenseless to criminals because they are extremely under armed (Update).
Certain weapons unfairly labeled as illegal “assault weapons” have also received an excessive amount of regulation because they have been deemed too dangerous for civilian ownership. Assault weapons that had previously been illegal under The Federal Assault Weapons Act of 1994 do not pose serious threats to public safety. The Act was allowed to expire under a "sunset" provision in 2004, but response is needed to keep it from being reenacted (Assault). Assault weapons are too large to conceal, thus being very undesirable to criminals. Law-abiding gun owners purchase "assault weapons" because they are useful in sport and target shooting and hunting. Gun control activists and supportive politicians made the assault weapon laws very stringent, including many moderate weapons with very little threat to public safety, making many popular hunting and sport rifles illegal. Another important piece of the assault weapon regulations is the large-capacity clip ban. Magazines that hold over ten rounds of ammunition were banned under the assault weapon law. Larger clips are in fact very important to legal gun owners because of self-defense needs. Police officers and military personnel carry magazines that hold more than ten rounds for protection reasons, showing that law-abiding citizens should be able to receive the same amount of protection from their weapons (Assault). 
Military reserve and National Guard troops need guns in order to train while they are not fighting overseas. Reservists and other non-active soldiers often train as civilians with weapons such as the AR-15, similar to the M-16 active-duty weapon, that had previously been illegal for personal ownership under the assault weapons ban (Assault). Soldiers need to be able to practice with guns that are as close as possible to the actual guns that they will be fighting with, in order for them to stay battle-ready, so that they can successfully protect the country.
Gun control activists are also misconstrued when they cite school shootings as reason for more gun control laws. They believe that with tighter gun regulations, school children will be safer, and not fall victim to tragedies such as those at Virginia Tech in 2007 and Columbine in 1999. The gun is usually blamed for school shootings, but, in fact, it is far more common that media and student's emotional and social situations are more to blame for school violence than guns, which could easily be replaced with homemade bombs or knives as the weapon of choice. 