It's a solid concept - we did initially consider Spread as the main benefit of spending Reloads, but that wasn't particularly satisfying compared to the flexibility.
The cost might need adjustment, as 2 Momentum is the cost of the Devastating Blow Momentum Spend, which does exactly the same as a Dark Symmetry Icon on a Spread 1 weapon (extra hit on a random location for half damage). Further, higher ratings of Spread are extremely valuable, as they can produce massive numbers of hits, and with a powerful weapon and/or against weaker foes, this can produce terrifying results. It's also worth remembering that multiple instances of the same quality, if it has a rating, stack - if your attack already has Spread 1, then something that gives it Spread 2 will produce Spread 3, so each of those Dark Symmetry Icons is giving you three extra hits. For that reason, I'd avoid the "Spread 2" option entirely.
Consider a Nimrod Autocannon (2+[DS]8 damage, Armour Piercing 1, Spread 2), using three Reloads and wielded by a character with Awareness 9 (for an extra +[DS]1). Twelve dice, so an average of 8 damage (including the static value), two points of Soak ignored, and four extra half-damage hits (4 each)... and that's without any Momentum spent. Level that against a mob of 5 Undead Legionnaires, and that's a dead mob. Per your suggestion, three Momentum on that could either be +3 damage (main hit goes to 11, extra hits go to 5 each: a net gain of 7 damage), or an extra Spread 2 (for Spread 4 in total, for 8 bonus hits: a net gain of 16 damage). Stacking up lots of Spread, particularly on weapons with Armour Piercing and/or Vicious is a good way to tear down cover as well.
You'd get similar, albeit smaller, results from something like a Panzerknacker rifle (which gains Armour Piercing 1 and Spread 1 whenever it spends one or more Reloads), an MG-40 (or any of a range of Bauhaus weapons), or any shotgun with a mode above Semi-Auto (the Mandible, SG7000, or Zhukov 4, just in the corebook).
Game Development - 2D20 System
System Design - Star Trek Adventures
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