What's the best short to medium range automatic rifle?

-Assault Carbine - Great ammo variety and versatility.

-H&H Tools Nail Gun - Great for stealthy head shots (with appropriate perks it can be a beast) as well as an interesting over-penetration effect.

-Automatic Rifle - It is a hell of a lot of fun to use the peepsight for close range headshots, especially when paired with Implant GRX (rank II with Chemist and Day Tripper). The spread may stink, but the high damage per shot make it killer against just about anyone you come across. Also, the poor item health can be overcome by having Raul (with Full Maintenance) in your party.

While these aren't the best weapons stat wise, I've built too many characters revolving solely around having the highest possible damage output...and honestly? They just weren't fun. Those three? Fun as hell.

Id have to say the BAR from dead money which is called Automatic Rifle in the game though it requires a high gun skill of 100 and 8 str. its uses 308 rounds and can tear up [censored] pretty damn fast.

For reall fun load up boone with the BAR and 1000rds of 308jsp and then sit back and watch the fun unfold

If you have a high enough strength and guns skill, get the LMG with extended mags. pretty good.