Combustable cases offer the benifits of caseless rounds without the disadvantages (problems that plagued the HK G-11 rifle).
My next concept is a sniper rifle that fires a laser-guided bullet which homes in on an infrared laser (so as not to be visible to the naked eye).
For years now they have had a counter-sniper system installed in some vehicles that detect an oncoming bullet by radar and the system aims an automatic cannon (20 or 27mm) at the target and shoots back in about 2/5 of a second. The sniper doesn't even hardly have time to duck. They were using them in Bosnia ten years ago.