Weapon technology progressed after the 50's in Fallout. It's not too far fetched to think they'd make some modern type regular firearms since they made energy weapons.
Neutral type companions will probably stick around. I could see Cass, Rex, Raul, Veronica, and Lily not caring. Boone is who you have to watch out for. Arcade is a moralist but who knows how much.
http://forums.bethsoft.com/index.php?/topic/1116391-411-interview/page__view__findpost__p__16396036
Sawyer on the ARCHIMEDES laser at the Beth forums:
Glad it's not overpowered.