I hate to bust your balls over this, but alien alloys wouldn't make a good material for armor piercing ammunition. You want a dense material, but alien alloys are light.
I don't see anything in the aliens' arsenal that we could use to improve the power of our projectile weapons' technology. On the other hand, their lack of understanding of such technology is something we could potentially use against them. Maybe with alien alloy barrels for improved strength, we could make very high-powered projectile turrets that have incredible penetrating power, and the aliens' heavy armor might prove weak against this technology.
I understand your objections, but it's mostly for gameplay balancing.
However, the idea behind this is:
1) In the game, the alien alloy process is using electro-gravimetric and magnetic annealing to create strong alloys in ways that could not be done before, using elements found on earth.
2) Expanding that idea, this process could be used to create rounds that combine both the density of lead and the hardness of titanium or diamond carbon.
3) Also, this manipulation of elements on the molecular level allows for the creation of hepta-octanitrocubane, a powerful explosive that is incredibly difficult to synthesize:
https://en.wikipedia.org/wiki/Heptanitrocubane It's RIGHT in the mod itself if you read:
"After trivial changes were made to the standard X-com assault rifle, the new alloy ammo can be fielded with the assault rifle without requiring a redesigned weapon. The enhanced hepta-octanitrocubane propellant and alloy 'sandwich' bullet design enhances both armor penetration and wounding power."
