After hours and hours of flying the lib, I have found that if you have 1 or 2 dedicated gunners w/ you, it's best to ask them which main gun they prefer rather than just say "hey I have this gun, who want to man it". Some people are just better w/ doing 2 pops at a time w/ the Zeph rather than 1 then reload w/ the dalton. Now the Zeph does have a longer reload time thus the 2 pops at a time making it a bit more accurate for inf kills while the dalton is more for armor column. In general I'm going to pull my Lib w/ the Zeph unless there is a good size enemy armor column that needs some death. Today there was a small base w/ enemy vehicles that had squad mates pinned down. after 1 min w/ my dalton over head there were no more vehicles and the squad broke out the music and dancing girls.
I love headshotting infantry, especially MAX suits, with the Dalton. I had a MAX guy private message me "You, sir, are surgical with that weapon." I don't seem to do as well with the Zeph.
I seem to be a good shot with both. Personally I don't care whats on the lib, as long as the round explodes when it hits the ground, tank, person, plane, or whatever.
