This subclass is a mixture of a few thoughts and is based on the use of a homebrewed Greatbow that uses modified javelins as ammo. It was originally designed based on the Unearthed Arcana Revised Ranger but this one is based on the version in the PHB. It is untested.

The Greatbow

At 3rd level, you gain one of the following features. You obtain a Greatbow and 15 Greatarrows with a modified quiver for your ammo. You are also able to craft Greatarrows using javelins and leather. Crafting requires a short rest. Magical javelins can be modified into greatarrows at the discretion of the DM. Stats for the Greatbow and Greatarrows are as follows.

Name	Cost	Damage	Weight	Properties
Greatbow	Unique	1d12	6 lbs.	Heavy, Ammunition, Range (100/400), Two-Handed, Special*
Greatarrow	Craft (javelin)	1d6 (when wielded as a weapon)	2 lbs.	Thrown, Special**

*The greatbow uses Strength for it’s ranged attacks. It uses the Greatbow ammunition and cannot use any other type of ammunition.

**The Greatarrow is the same as a javelin in every way except it has a notch and flights made of leather. It can be used as a javelin and any javelin can be crafted to become this type of weapon. Recovery rates of ammo may be adjusted at DM discretion. Maximum number of Greatarrows that can be crafted during a short rest is 15. Supplies are at the DM's discretion but recommendation is a limitation of needing to purchase or find javelins (spears may be a questionable substitute).

Special Shots

At 7th level, you gain two of the following features of your choice. You gain a number of Special Shot dice equal to your Wisdom Modifier (min. of 1). Special shot dice are a d4 and increase in to a d6 at level 11. You also learn two more special shots at level 11. These features can only be utilized with ranged attacks from the Greatbow. You recover special shot dice on short rests.

You declare the use of a special shot on a hit unless otherwise noted. You can only use one special shot per turn.

If a DC is listed for the feature, it utilizes the Spell Save DC for the Ranger.

Heavy Shot

The creature rolls a Strength saving throw. On a failed save, it is pushed back 15 feet. On a critical fail, the creature is knocked prone. This can only be used on Large or smaller creatures. Add the special shot die to the damage.

Master Shot

 Uses 2 uses of the special shot. Roll the special shot die and add it to the attack. If the roll brings the value of the d20 roll without other modifiers to critical range, you deal a critical. You also add the special shot die to the damage roll regardless of if you achieve a critical. Do note that this feature only can be activated if you are already hitting. This means that it does not increase the odds of hitting. It can only give the chance of forcing a critical.

Pinning Shot

The creature rolls a Con Saving throw. On a fail, it cannot move. It can use a bonus action to make a Strength Saving throw on each turn to try to unpin itself. Add a special shot die to the damage.

Power Shot

Add two rolls of the special shot die to the damage of the attack.

Siege Arrow

Damage from this attack gains the siege effect (double damage to constructs, objects, and buildings)

True Shot

This is declared before the attack. Add the special shot die to the attack roll. Your range is also improved for this attack to be the same as the Longbow. 

Hold the Ground

Gain proficiency in Heavy Armor (Note that this is not something most rangers would use. This is unique to this subclass style of fighting)

A master of the Greatbow does not need to flee or move about the battlefield. They hold their position and rain down heavy spear arrows on their foes. If you do not use any movement in a turn, you gain advantage on attack rolls.

Improved Critical

A critical strike now occurs on a natural 19 and 20. This does work with Master Shot. See Special shots for improvements to features.

Shield Breaker

At level 15 your most powerful blows can destroy shields and break armor. On a critical, the creature that is being hit must make a Con Saving throw against your spell save DC. On a failed save, decrease the AC of the enemy by 1d4. Functional changes determined by DM (might damage or destroy a shield. An enemy might replace a shield to restore part of their AC. DM decides what is causing the decrease in AC).