To shorten the distance between the screen and the gun i'm planning to use a wide angle lens taken for a mobile phone camera upgrade kit, do U think that this is a good idea?
Been there! Tried that! Got the T-shirt!......
It won't work, because of the fisheye distortion you'll get from that lens setup. You also need a further lens system to remove the problem, and that's when it starts to get very expensive. The problem I'm finding, is that to work effectively, the lenses have to be as near to optically perfect as possible and that's what costs the big bucks.
Still on the case with that one....... You could give it a try and see if you get a better result than I did though.
Best Regards,
Julian (Fozzy The Bear)