i found that is you have the least amount of points you get a good gun. also i found that there is a better chance of a ray gun with the least amount of points on your last spin.

I actually get ray gun quite often, I usually just press x as the darkest shade of gold comes (does take lots of practice) but usually i get it after the teddy bear comes and moves the box.
If you can't get the dark gold thing just save up lots and make a crawly guy with a grenade and buy tons of guns from the box.

i get it allmost every time. idk y i just do