Never treated a gunshot wound. Have treated several wounds caused by explosions and shrapnel.
The most effective method of stopping/controlling bleeding i have found is rolls of Kerelex (5"wide). Place one on the wound, in the case of a full penetration one on each hole. Take a third and wrap it as tight as possible around the limb and the Kerelex.
A less expensive, but equally effective, alternative is Kotex (unscented) pads and an ace bandage.
The pads are sanitary though not sterile they are highly absorbent and cause clouting. The ace bandage will apply effective pressure.
Off subject but in the same vein. Burns are a serious threat to us as many engage in camping and other outdoor activities. One of the best methods for treating a major burn is to apply foamy unscented shaving creme. The foam seals the burn cools the area and protect it from infection.
When the burn victim arrives at the hospital they simply wash it off.