Say a wild boar for instance is brought to bay by the first shot.
He cannot be approached with safety to use the knife, he is killing the dogs, he has to be shot again.
Now you do not want to fire your rifle, which makes a boom like a cannon, as that would disturb the rest of the beat.
If you have a pistol which shoots a big .44 calibre ball with a reduced charge of powder you can go close up to the boar and kill him without making much noise.
If a wounded animal gets you down, a pistol which lies close to your hand may save your life, and if it shoots a heavy charge and is rapidly fired several times into his body, it would stop most animals except an elephant or rhinoceros.
A rifle can be lost in falling or lain on, the length of barrel prevents it being used at close quarters.
The objection to carrying a pistol in big-game shooting is that every possible ounce in weight has to be saved, especially in a hot climate. The pistol is so much extra weight and when climbing amongst rocks it is a great nuisance. To be of any use against dangerous game the pistol must shoot a big bullet.
In the instance of the wild boar, I mentioned a reduced charge but my idea is to carry the two sorts of cartridges and to have the automatic loaded with full charge cartridges, but if game has to be finished which is not endangering your life, I recommend putting in a gallery charge cartridge for this particular finishing shot so as not to make more noise than absolutely necessary, and not to disturb other game which may be near.
An automatic pistol built for a big charge will not function with a reduced charge. Such a charge does not give enough recoil to introduce the next cartridge and an automatic only works properly with the exact load it is designed for. With a reduced charge the automatic pistol, after the shot, remains half open.
If the magazine and also the cartridge which is in the barrel are first taken out, the gallery-load cartridge can be put in the barrel and fired. Afterwards the loaded magazine can be put back again and the pistol is ready to shoot the heavy charge.