the only projectile that makes sense would be shock since its a lightning bolt and we see it in nature all the time. frost and fire dont make any sense being projectiles. are you conjuring a frost ball from the moisture in your body or the air. if its your body then your going to get thirsty real fast and if its from the air i hope you dont plan on using ice magic in a desert. what allows the fire to keep burning between you and the target. are you using your own methane to keep it burning. does that mean im shooting flaming farts from my hand? a fire attack should simply be focusing on an enemy and causing them or their armor to heat up. after a couple of seconds then flames will appear. a good image of this are the guns they used in Logans Run, although it shouldnt be as fast as those and the flames could be bigger. think of using a magnifying glass to burn ants but quicker.
ice attacks should be the caster focusing on the target for a couple of seconds and then the target slows down and ice starts to form over the target. the higher the skill the quicker the slow and freezing takes place and the larger the enemy that can be frozen. same with fire attacks. the higher the skill the more quickly flames appear and the hotter they get (more damage). you could even make it so that low level flames are yellow and the highest level flames would be white or blue. it would be nice if materials matters such as robes and leather armor being highly susceptible to flames but resistant to frost and metal would be resistant to flames but would make it easier to attack someone using frost. thats probably asking for to much.
lighting would be a good stun attack with less damage unless the target is in water or something but it could be a quicker attack. the SMG version of magic attacks. lighting could also have the advantage of chaining.
it would be nice to have a game with a well thought out magic system that makes sense on a basic level even if you have to make up stuff here and there. i can barely control moving a scroll around with telekinisis but somehow im able to pick intricate locks with my mind.........how the hell does that make any sense.
i guess games will alway have magic for dummies.
i really hate taking chemistry and physics in college..........it makes silly things like these stand out even more.