Skill Points

Skill Points come with every weapon. When you reach a certain number (It goes higher every time you reach it), you can get an upgrade and the weapon's rank goes up. Skill Points are global, meaning that if you have an AK-47, lose it somehow, then get a new one, you will have the same skill points on that AK-47 as your old AK-47. You can choose the upgrade you want.

Promotion Amounts
These numbers are the ones you have to reach for a Weapon promotion (rank-up) and an upgrade.
 * Promotion 1: 100 Skill Points
 * Promotion 2: 450 Skill Points
 * Promotion 3: 900 Skill Points
 * Promotion 4: 1,450 Skill Points
 * Promotion 5: 1,875 Skill Points
 * Promotion 6: 2,000 Skill Points
 * Promotion 7: 2,400 Skill Points
 * Promotion 8: 2,750 Skill Points
 * Promotion 9: 3,000 Skill Points
 * Promotion 10: 3,400 Skill Points
 * Promotion 11: 4,100 Skill Points
 * Promotion 12: 4,900 Skill Points
 * Promotion 13: 5,200 Skill Points
 * Promotion 14: 6,000 Skill Points
 * Promotion 15: 6,500 Skill Points
 * Promotion 16: 7,000 Skill Points
 * Promotion 17: 8,000 Skill Points
 * Promotion 18: 9,000 Skill Points
 * Promotion 19: 9,000 Skill Points
 * Promotion 20: 10,000 Skill Points

There are 20 promotions total (as you can see), so a total of 20 weapon upgrades. There are some upgrades with all weapons, and some upgrades with only specific weapons.

How to get skill points
You can skill points by the following:

Kill an hostile player: +30 Skill Points

Kill a hostile NPC Soldier: +20 Skill Points

Assist a friendly: +10 Skill Points

Get a headshot: +40, +30, or +310 Skill Points (20/30/300 for the kill, 10 for the headshot)

Kill an enemy General/Commander in Chief): +300 XP

More to come!