The CTOL F-35 internal gun is a 25mm vs the normal 20mm too. The carrier variant of the F-35 also uses the gun pod.
A 16 guy! I have 17 years on 16s too, with 2 on F-15s. Currently working the F-35 program as a civilian. It's cool, but I prefer working the F-16 over everything. It's THE crew chief's jet. Given the opportunity, I'd jump the F-35 ship for it (any block).
As for the topic, any bullet will hurt any aircraft. Skins are typically just aluminum, titanium, or composite, nothing cosmic. What damage a .50 would do is a matter of where it hits & what it hits under the skin. Jets are a maze of wiring harnesses, ducting, & tubing, along with fuel cells and components. All critical systems are redundant though.