I know that the movie is likely from the '80s, possibly from the '90s. It may contain either human like aliens or some form of time travel. One of the two main characters - maybe the bad guy - is a hair-band wrestler type with white hair and - I believe - crazy looking eyes, like solid colored, lacking irises, or something similar. He is most likely some form of bounty hunter. Most importantly, I remember that the 'cool weapon' was a fully-automatic pistol that utilized explosive ammunition.
I think that this might be Dark Angel (1990 film) (apparently this is also known as 'I come in peace' but produced and released outside North America as Dark Angel)?
It has aliens with explosive ammunition (who are terrible shots), the main bad guy alien is a drug dealer from space being chased by an alien police officer.
The alien police officer is killed and hands the case over to an American policeman played by Dolph Lungren.