Has a gun that shoots pellets that grow into giant thorn bushes in seconds, bad guys were empty black suits of armor with arm blasters, and they came from a giant black arch/doorway thing that would phase in and out. Can anyone help?

I remember a movie that I saw about 15+ years ago that was about a guy that had a pretty big death ray. He used it on all types of things such as a train and a submarine I think. I can remember one scene where there is a couple in an empty commercial train car having sex and the laser death ray...

I remember a movie that I saw about 15+ years ago that was about a guy that had a pretty big death ray. He used it on all types of things such as a train and a submarine I think. I can remember one scene where there is a couple in an empty commercial train car having sex and the laser death ray...

The movie starts with a flying saucer landing in an area that looks like a desert type area. Three space men get out and walk away from the ship. They look just like us and two are holding ray guns. It seems that they have come to Earth to execute the third man. There is a sudden comotion in a cave...