Was this James Brady the one shot when Reagan was, the one for whom the gun control group was named?

There are many Bradys. This author may easily be some other man.

I don't know why the Marines banned officers carrying their own sidearms. Marine pilots and other aircrew did have S&W .38 revolvers, mostly leftover Victory Models from WW II. Navy and Marine airmen carried those well into the Vietnam War and maybe later. Many were also furnished to the USAF in those years