A Tiefling imbuing an arrow with ki, then letting it loose as it strikes clean through their skull. A Gnome shooting a crossbow bolt into a goblins foot right in front of it, and then pummeling them in the face with Martial Arts. A Wood Elf channeling the air in it's lungs to fire it off into a small projectile, hitting a squirrel high up in a tree so they may feast on the squirrel as a snack. A Monk of the Horizon learns the ways of ranged combat and uses it to their advantage, whether from afar or up close and personal with their enemy. 

Zephyr Punch

You may take a deep breath and, channeling all your breath into a cannonball of pure air pressure that you can fire off at a target.

You gain a new attack option that you can use with the Attack action. This special attack is a ranged spell attack with a range of 30 feet. You are proficient with it, and you add your Dexterity modifier to its attack and damage rolls. This attack does thunder damage, and it's attack die is equal to your martial arts die. This attack also counts as a "monk weapon", meaning you may follow up with an unarmed strike after the Zephyr Punch.

Your Zephyr Strikes do not have disadvantage on attacking a target within 5ft of you. 

Arrow to the Face

At 6th level, Horizon Monk's become experts at using ranged weapons up close and personal, as well as channeling their ki into their projectiles

-Being within 5 feet of a hostile creature doesn’t impose disadvantage on your ranged attack rolls.

-You may spend 1 ki point to imbue your ranged weapon, increasing it's damage by one roll of your martial arts die. 

-Your ranged weapon attacks become magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage.

Quiver of Air

At 11th level, your skill with imbuing projectiles with your ki increases, as well as your ability to launch Zephyr Strikes

-A projectile that is imbued with ki becomes encased in a layer of wind. The projectile will continue until it hits the end of it's normal range. It will continue unless it is stopped by magical means. 

-Your Zephyr Punch becomes easier to channel and unleash. With the unarmed strike you get as a bonus action from your Martial Arts ability, you may substitute it with a Zephyr Punch.

Bouncing Betty

At 17th level, you master the ancient art of ending your opponents life with the loosening of a single projectile.

-Right before you hit a creature with a ranged weapon attack, you may imbue that weapon with 5 ki points, completely coating it in a cloak of wind. If the weapon hit's the target, the target becomes marked by the projectile. The projectile will then, depending on it's size and on the caster's choice, either ricochet within the body or fly around just outside of the body. Once the projectile hits the target, the target must make a wisdom saving through. If the target succeeds, it takes 12d10 force damage as the bullet looses it's wind coating and ends up lodged in the target. If the target fails, it is reduced to 0 hit points. 

Yes, projectiles include thrown weapons

If the projectile hits and the target fails the saving throw, there is no stopping the projectile until the target is dead.