Fallout: Equestria - Ideas on general gun usage
Usage in different races
Earth ponies have to rely on a mouth grip or a battle saddle on all weapons, since they have no means in lifting them in any other way.
Mouth grips are mostly designed with the abilties of Earth Ponies in mind. They have no problem with the kick of the gun, since they are physically more powerfull and resistant then other races. They can handle every firearm up to a medium sized shotgun with ease, using a mouth grip.
However, anything larger than that can only be handled with a battle saddle. Though most Earth Ponies could probably handle the kick, there would be a massive problem with balancing and aiming a gun that big.
Battle saddles have the same controls as the mouth grips in the control bit. Although some individual ponies attach some special controls for things like ammo type change to it (for example Calamity).
Most Unicorns don't have to bother about the size or the kick of a gun, as long as their levitation spell is strong enough to handle it.
If their levitation spell is not strong enough however, the are forced to use the same techniques as Earth Ponies. Beeing physically weaker and less resistant reduces their ability, to carry heavier weapons, even further in that case.
Enclave Pegasi mostly use energy weapons with nearly no recoil at all. Therefore, they can handle energy weapons around the same size as Earth Ponies are able in terms of conventional weapons.
If they have to handle convential firearms however, they have the same problems as Unicorns do. They are also restricted in using larger mouth grip weapons in flight for aerodynamic reasons.
Griffons have claws which work like hands, so they are practically able to use all weapons.
Zebras undergo special training in weapon handling and use specially crafted weapons. They use most of their weapons with their hooves. There are no known cases of a Zebra handling a weapon bigger than a minigun or a shoulder operated rocket launcher, that would require a battle saddle.