What does leveling up weapon mods/attachments do?

Solution 1:

After searching for some time I found a forum post from 2012/2013 which discusses the differences between weapon mods.

As you know, weapon mods affect your weapons in different ways:

• Hunter's Mod - Decreases gun sway and recoil. Smaller magazine.
• Warrior's Mod - Increases damage and penetration. Decreases accuracy.
• Marksman's Mod - Longer range and improved accuracy. Slower handling.
• Ranger's Mod - Faster reloading and aiming. Less ammo carried.
• Stalker's Mod - Larger magazine. Slower movement and weapon switching.

And all of these mods have five levels Mk1 through Mk5, for a total of 25 mods available through decoding.

On the Ubisoft forums user Detrooit asks (grammar fixed):

I know the difference from the Weapon Mods, and every Mod has an Mk Level from 1 till 5. After my decoding I get, for example, the Ranger Mod Mk5, but I still have the Ranger Mod Mk2. The level is changing, but what does it exactly effect?

And users KasDaDon21 responds (grammar fixed):

I have studied an I have a found an answer. As you know each type of mod does something different. The mod does what the description says, but the higher the Mk the stronger the effect of the mods description.

This would mean a gun modified by a Mk1 Hunter's Mod, which decreases weapon sway, would still have more sway than the same gun modified by a Mk5 Hunter's mod.

Earlier in the forum post users also confirmed that upgrading the Mk of the mod does not decrease the negative effects of the mod. For instance, the Hunter's mod, which also decreases magazine size, would maintain the same small magazine size regardless of whether the mod is Mk1 or a Mk5.

In summary, a Mk5 mod increases the benefits of a weapon mod with no effect on the downsides. A Mk5 mod will be objectively better than a Mk1 weapon mod of the same category.