I'm a very basic noob in Blender, and I've been unable to find a solution to my goals.
I have a basic model and I'm adding a texture, so far so good. The screenshot is a mock-up, not the real thing, but it serves a purpose.
There is often a lot of wasted space in a texture, so it looks something like this:
I see some lovely uvmaps, with nice clear space around them, like this:
My question is, essentially, how can I achieve something more like the gun model uv map / texture using default or freely available Blender tools for 2.79 or 2.80?