The Heartsplitter is a Relorian sniper rifle design. The original used was just a little less powerful than a Barret .50cal. That is the design that Hiren had access to.
There's a large difference between a standard rifle, and a dedicated sniper rifle Hawkeye.
As for the character himself, you still haven't changed the magic. And, because the Relorians, particularly Nisorin, had such a particular dislike for Hiren, they'd have made sure to remember his magical signature, so they wouldn't need his name to recognize him.
Because you've modified the Sunslayer so much, you'll have to request it as a new ship type. Due to the fact that he is a returning character and the circumstances behind his procurement of the Sunslayer are valid, I will allow the instant creation of ONE of the new ships once both the tech request and Hiren/Valor is approved.
However, because Hiren does not have the blueprints to the Sunslayer nor the technical and scientific expertise to have been schooled in Relorian spacefaring research, this one ship will be the only one of its type you will be able to request until he gets it to a group that can handle that sort of thing, and they study it for at least five days after you POST them beginning to study it. During that period of time, unless the research crew is on board, you will not be able to use the ship because it will have to be docked for them to perform their research.