Here in Indiana, the minimum age to get a LTCH (License to Carry a Handgun) is 18 and we have no training requirement (it's been this way for decades) and we don't seem to have any more issues than any other state.
As to whether or not those aged 18-20 should be allowed to carry, consider the following: at 18 years of age, one is old enough to enter legally binding contracts, get married without the consent, or even knowledge, of his/her parents, and be prosecuted and punished as an adult for any crimes that he/she may commit. While it is true that, for the most part, those who join the military are more closely supervised than civilians, a person who joins the military also takes on a great deal of responsibility in that he/she chooses to give up a good amount of his/her freedom while enlisted and that he/she will be expected to fight and possibly die for his/her country should the need arise. So great is the responsibility associated with military service that we do not allow those under the age of 18 to enlist without the consent of his/her parents or legal guardian. Finally, even though there has not been a draft since the Vietnam War, young men are still legally required to register with Selective Service at age 18 and, if the draft were to be reinstituted, could be conscripted into military service against their will.
So, it seems to me that, at age 18, people in this country are old enough to bear all the responsibility of an adult, but they are still denied certain rights because they are "kids". I have yet to meet anyone who magically turned from a pot-smoking delinquent or beer-guzzling frat-boy into an upstanding responsible adult at the moment the clock struck midnight on their 21st birthday. Are there young people who should not be trusted with a firearm? Sure there are but there are also people well into their 40's, 50's, 60's and beyond who should not be trusted with a firearm or even a pointy stick for that matter. It simply boggles my mind that we tell someone that he/she is old enough to bear all the same legal responsibilities as someone multiple times his/her age, but in the same breath and with a straight face tell that person that he/she can't carry an effective means with which to defend his/her life and the lives of his/her loved ones because he/she is still a "kid".
I have always considered self-defense to be the most basic of all human rights. As such, I simply cannot rationalize how a person can be legally cast out into the world to fend for himself/herself with no one legally required to protect him/her at 18, but at the same time deny that person the right to carry a handgun to defend his/her own life with until the age of 21.
