no it doesn't need to be kept at the arms room. He will have to register it on post. I am not sure what it takes to buy a gun. I am not usually there when my hubby buys his, but an ID is for sure then he will have to fill out a back ground check to (you have to do that anywhere you buy a gun).
My husband bought his off post I think at the gun place in Ogden when we lived there. He isn't inside right now but if im correct the gun place off post accepted the orders to Kansas and both military I'd and drivers license. I think that was it. And because he was in military and provided his orders they didn't do a background check. But in sure things have changed and maybe more strict on buying and what is needed to buy one. Not sure about what you would need of you purchased at px. Rather on or off post they are supposed to be register with post if your military. Ours were registered with post even tho we lived off. And their was a paper my husband had to carry for anytime he had them in his vehical to Hunting or to the ranges incase he got pulled over or had a random vehical inspection when he went to post.
1. He needs his commanders permission to keep it at home on post. (its in the reg) 2. it needs to be registered, take your form from the PX to the MP Station and get another form that needs signed by his commander. Keep a copy with the weapon and turn in a copy to the MPs. The PX form is good for 5 days. 3. DO NOT bring the weapon to the MP station, it makes people nervous. 4. The weapon and ammo need to be seperate when you transport it, have a copy of the registration with the weapon. 5. If you are stopped by the police some of your first words should be "I have a weapon in the car, its registered and unloaded"(on post) 6. A concealed Weapon permit from any state is NOT valid on a federal installation.