Advance
Caliber Standardization
With artillery's growing importance on the battlefield, the number of firearms kept increasing. But because each gun was made separately, it also required great effort to resupply. In 1544, in an effort to mitigate this, Emperor Charles V declared that there would be only five calibers of guns, while King Henry II of France set the standard of calibers at six.
Advance tree
The game files don’t say where this goes: it has no requires, so the game places it in the 
Reformation tree itself.
Modifiers
Supply Limit+10%