AS7-RS Ungainly Sniper 2 (3x ER PPC, AC/20, 2x SSRM2, STD 275)

AC/20 Version: lot more heat, slightly more armor, and less fragile.

http://mwo.smurfy-net.de/mechlab#i=18&l=43dea13683b42afc90c3a15df6416cfb55923411

Group 1 3x ER PPC
Group 2 1x AC/20
Group 3 2x SSRM2

Chain-Fire is your friend