Mounted vs. Dismounted
When is it a good idea to have the shotgun pre-mounted? There are times this is a fabulous way to shoot.
For new shooters, a pre-mounted gun is almost a no brainer. Having the gun pre-mounted allows the shooter to learn proper stance, how to get the gun in the correct position in the shoulder and on the face, and to learn to focus on the target. As a shooting instructor, I almost always start new shooters with a pre-mounted gun, with the intention of getting them to a lower gun as soon as possible for better target acquisition and peripheral vision. It also takes away the tendency to try and “aim” the shotgun, vs. pointing it.
A pre-mounted gun is also often used when a target needs to be taken sooner vs later, as sometimes presented in true pairs and/or when the speed and trajectory of a target do not allow much time for a solid gun mount. A pre-mounted gun is great for really any fast moving bird. For example, for any fast outgoing bird, a pre-mounted shotgun is a great idea. The targets are getting away quickly and by taking the mount out of the equation, you will get on the target faster, removing the random gun movement that leaves a lot of room for error. Likewise, targets that are fast crossers, quartering away or screaming rabbits are also great candidates for a pre-mounted gun.
The game of trap is almost always shot with a pre-mounted gun. Generally skeet shooters also use a pre-mounted gun.