Sniper

Rogues that train with the Firearms expertise in precise shooting from far range and rely on penetration of black powder weapons to wound vital points. Learning from this effect they discovered how to injure enemies. They prefer fighting from a point, giving up their mobility, but surrounded they still can cut ferociously. Such snipers might be deadly killers, but also irreplaceable allies in fight against monsters of colossal size.

Training in Firearms

Starting at 3rd level You learn effective use of black powder weapons and can improve Your accuracy against distant targets while standing still. You gain proficiency with Firearms. In addition, you have created or otherwise modified another firearm into a high powered rifle. This rifle is a two handed weapon, with a base range of 120ft and long range of 360ft. At 3rd level, this rifle deals 2d6 piercing damage on a hit (this damage increases to 2d8 at 5th level, 2d10 at 10th level, and 2d12 at 15th level). The rifle holds 6 bullets at a time, requiring the use of an action to reload once the last shot is fired. However, this rifle is a noticeably large tool, making staying out of sight while using it a challenge. As part of taking the hide action while you're wielding a firearm, you become prone. 

You also have learned how to utilize the long range of firearms to your advantage. You gain an additional rule that affects your sneak attack; You don’t need advantage on the attack roll to use your Sneak Attack against a creature if you are at least 30ft away from it, and you don’t have disadvantage on the attack roll. All the other rules for Sneak Attack still apply to you.

Killer's Sight

Snipers master their senses to see hidden targets and perfect their scouting. When You choose this archetype, You become proficient with Perception skill. You double Your proficiency bonus for checks made with that skill. If You already are proficient with Perception, You become proficient with different rogue skill. If You already have expertise with Perception, You gain expertise with different skill You are proficient with.

Combat Slide

Starting at 9th level, you can prepare yourself to fire at a moments notice. A number of times equal to your intelligence modifier (minimum of 1) per long rest, you can use a bonus action to enter into a slide, moving up to half your movement speed in a direction of your choice. This movement does not provoke opportunity attacks. 

Distant Killer

You don’t have disadvantage on attack rolls against prone targets and complete darkness doesn’t pose disadvantage on your perception and investigation checks in range of your Darkvision. Additionally, when you deal Sneak Attack using Firearm, you gain advantage on first attack with your Firearm that you make on your next turn, provided the target is still 30 feet or further away from you. 

Crippling Shot

When You reach 17th level You learn alternative ways of dispatching opponents. When You deal Sneak Attack to a creature, You can reduce it by 3d6 to impose one of the following effects on the target. You can use this feature multiple times per Sneak Attack, as long You have damage dice to forfeit. You can impose each effect once per attack. The Save DC of any saving throw forced by this feature equal 8 + Your Dexterity Modifier + Your Proficiency Bonus.

• Dazzle - Target makes Constitution saving throw. On a fail all attacks it makes until end of its next turn are made with disadvantage.
• Paralyzing Pain - Target makes Constitution saving throw. On a fail its speed is halved and it makes Strength and Dexterity saving throws and ability checks with disadvantage. It can repeat the saving throw at the end of each of its turns, ending the effect on a success.
• Open Wounds - For a round, each weapon attack that hits the target deals an additional die of weapon damage.