One favorite topic seems to start something like this:
"I am going to join the Army/Marines and if I get sent into combat, I am going to carry rifle x/handgun y/ammo z. All my buddies say that is what they recommend and the gun magazines have great writeups. I also have seen movies where the hero used those guns/ammo in fighting the terrorists/drug dealers/bad guys."
I don't know quite how to enlighten those guys that if they are unfortunate enough to sent into a shooting war, they will not carry any of those neat guns or that cool expanding ammo that the gunzine gurus recommend. The armed forces have the bad habit of issuing standard weapons and insisting that the troops carry them and not some cockamamie gun they saw on TV. They also tend to follow the Hague convention on ammo, even though we didn't sign it and our enemies are not soldiers of recognized nations.
Yes, there may be special units that have a wider latitude, but even for them there are rules, and they don't include the M1, M1903 or a .58 rifle musket, no matter how good they were "back then". Nor do they include some whumped up fictional movie gun or some one-off experimental that G&A is pushing this month. You will also not be able to bring back captured guns; that practice has been ended.
So, if you want to join the service, I will honor your courage and pray for you; I hope you succeed in your assigned mission, whatever that may be. I admit that my two years of military service did not include combat, and I will also admit that I am grateful for that. Had I been called on to fight, I would have, I hope, done so to the best of my ability, but I have not regretted not receiving the call.
But had I gone into combat in 1956, I would probably have been issued an M1 rifle; they would not have allowed me to build a time machine and get an M16.