Granted, I say this as someone the military said "thanks no thanks" to, so grain of salt yadda yadda
I would go further, if it was up to me. If it were possible, I would make it very difficult for a male to buy a gun before he turns 25. There's a reason why male car insurance rates are absurdly higher than females until their 25th birthday. If 18-24 year old men are measurably more reckless when operating an automobile, why entrust them with a gun? Yes, we arm 18 year olds in the military, but they have pretty intense training and supervision.
If we can trust them to defend our nation we can trust them to defend themselves. That said, clearly, that only applies to those who are soldiers. That also said, this is precisely why I think mandatory service would be good.
Not to mention it would give a paper trail for people who are truly mentally unwell to be noticed, tracked, and hopefully helped.
There's 0 chance this happens though.
The late conservative Justice Alito wrote that like all rights, the Second Amendment is not limitless. The chances of national laws that resemble those in Connecticut are realistically not very good. But hopefully more states will tighten their laws. Connecticut, New York and California are examples of states who's strict laws have passed Constitutional muster.
So far. Aren't some of them being challenged currently? I don't own guns so it's not something I keep up with, but I seem to recall hearing something about the possibility of SCOTUS expanding gun rights, which, holy shit, wouldn't that be an awful look.