If it cost the FBI over a million dollars to hack one iPhone, why would guntards fear the government will hack smart guns?
The Fifth Amendment means that a person can't be forced to supply a passcode, and indeed that's a particular problem for law enforcement when it comes to iPhones and iPads. iOS requires that a Touch ID user re-enter their passcode if a device is rebooted or hasn't been unlocked for 48 hours, which could potentially put data out of police reach.
The FBI has been managing to crack into some iPhones, but the techniques used may not apply to Touch ID devices, which have a "Secure Enclave" making hardware detours around encryption either difficult or impossible.
http://appleinsider.com/articles/16/05/02/los-angeles-court-orders-woman-to-unlock-touch-id-equipped-iphone-for-fbi