Survivalist's rifle + 12.7mm JHP ammo (GRA) = bye bye Automatic Weapons. 4 rounds to the face of a deathclaw makes it dead. No sneak attack. No critical hits.

The game just favors high base damage and/or high critical damage figures. Automatic weapons overall tend to be lacking in both, hence the high ammo usage needed per target. Automatic Rifle from Dead Money is the sole exception, but that has absurdly low item HP for such a weapon system.

Critical hits, higher range and not having to carry seven million rounds of ammo.

I don't know if this is off-topic, but, despite being a Guns character:

BLOOD-NAP IS CRAZY GOOD!

(It's also fun to look at, as you lunge with a power attack)