https://underrail.info/build/?HgcDCgMNAwfCoABtAAAAwqBQQE0AAFRqQiNMADcARgAoPCY7OSQVAkpHScKHKsOiw6RTwrXChcKmK-KlngXip7QK37w
AR. The king of firearms, mostly because it really needs very few feats to come online.
Full Auto and
Concentrated Fire. Add
Commando and
Ambush (for accuracy for your Concentrated Fire). Leaving you with a lot of feats and skillpoints to round out your build as needed.
So how does an Ambush AR build function in combat? Open combat out of stealth, cast Premeditation + TK Proxy if needed, burst fire ~3 times with Hornet (+1 for Commando), leaving you with MP spare. This spare MP is typically used to retreat because Ambush builds use light armor; but here is the spice:
Blitz. Blitz gives you an entire extra burst, but not on your first turn, but your second; you end your first with 4 AP to spare; next turn, Blitz + 4 AP is 109; enough for 27*4 bursts = 108. Alternatively, 90 AP (PTC + PTA + Vitality Powder) + 20 AP (Blitz) = 110, enough for 4 Hornet bursts turn 1. Not accounting for Rapid Reloader AP refund.
The extra Commando burst can either be a Chimera or the Hornet. Using a Chimera ups your damage by a lot, especially if its also equipped with Anatomically Aware Scope. Or you can use neither, and use a Grenade Launcher as your secondary. Especially because Blitz. 35 AP Launchers can be fired exactly 3 times with Blitz. Or 4 25 AP Launchers. You already can use 2 35 AP Launcher + 15 AP Throwing (with 85 AP). Actually nutty AOE potential, and this is from your backup weapon.
The other spice is Evasion.
25mm Concussive Grenades and Suppressive Fire massively limit enemy MP/AP, crippling melee enemies;
Evasion + Nimble + Shell Shock Cluster Grenades takes care of ranged ones.
Suppressive Fire with Spec reduces hit chance of enemies in cone by 20%. Add Precognition if needed, and you can actually reduce hit chance to the
minimum 10%. Remember Evasion applies before Energy Shields, so you aren't even that squishy. This works very well with Blitz, since if you Blitz you lose all your MP.
The only issue this build has it that its rather Skill-hungry. Chemistry is necessary to craft launcher grenades; might as well take to to full 112 for Thermobaric Launcher Grenades and MKV Grenades. You need shields and cloaking device, so Electronics; Mechanics for your weapons, biology for Hypercerebrix, Tailoring lategame for Infused Greater Siphoner Leather Armor/Boots. Then you need Evasion, Stealth and Throwing; as well as 55 PK and 70 TM. Leaves few luxury points to spare; you can't really afford to max out stealth for this reason, though you have no need to given your 10 AGI. While MT 140 can be useful; Evasion and high MP gives you a lot of breathing room versus groups; so you don't need to go all out on AOE Alpha Strikes.
Dropping Premeditation + 55 PK is viable too; and use Incendiary Ammo, Grenades and Launcher Grenades to light people up for Ambush. Practiced Parabola, Skinner, Interloper are all useful, as is Recklessness + Scrutinous (dropping Strider).
