Sam said:
Any legal firearm can be sent home via form 6 pt II
www.atf.gov/forms/download/atf-f-5330-3b.pdf
Sam - you're giving ILLEGAL advice. And you're wrong.
General Order 1 stated, in summary, mere POSSESSION of war souveniers or privately acquired guns, ammuntion, gun parts, weapons, military gear, etc. was illegal. (Minor exceptions for some TA50 gear such as helmets, pouches, insignia, etc.). If you were caught with an AK47 or pistol, without authorization, your goose was cooked.
Yes, I am aware of Soldiers holding on to these for mission specific purposes, backup guns for Spec Ops, etc. But that's not what we are discussing here. God save you if you're trying to send a gun home from theater. Nearly everything sent home was supposed to be inspected by Navy Customs, postal service, etc. It was all carefully searched, X-rayed, etc. Having gone through Navy Customs many many times, I can tell you that it was VERY thorough. You were stripped of all of your possessions except the clothes you were wearing. Everything you sent back in your ISU container was searched thoroughly by inspectors while you stood there and they dumped everything out and searched every nook and cranny for contraband. Then it was all packed up and locked and shipped. All of your 'luggage' was then sent through metal detectors and Xrays. Then you went through a metal detector (and on one of my trips, I went through an Xray back spatter machine). After all of that, you dumped all of your gear out in front of a Navy Customs inspector and they literally went through everything, item by item. (Funny story, a female NCO had to rummage through my VERY dirty laundry including socks and underware... poor woman...). I am also aware of cases where folks smuggled guns home and were later caught. They are now called "Inmate."
GO1 is punishable by law, and violating it subjects a military person to up to 2 years in prison and a Dishonorable Discharge under Article 92 of the UCMJ.
http://usmilitary.about.com/od/punitivearticles/a/mcm92_2.htm
Here is a copy of GO1, from 2006. This, or a version of it, was in effect in Iraq beginning with the invasion as far as I know.
http://www.militaryatheists.org/regs/JPGO1B-4.pdf
I do this for a living brother... and have plenty of experience both as a prosecutor (for the 101st Airborne Division and 5th Special Forces Group) and as a Defense lawyer (for I Corp) for many years.