Dagger at Efate has such an incident of a Broadsword being used in such a way as to collide with a planet.
However, logical inference would say that insufficient data coupled with the facts that ships do not travel at near c, nor are these weapons used in the OTU, is that there is some limiting factor as to why.
I love Niven, one of my favorite writers. I recall a dilemma Niven presented - well, more like mentioned in passing while on another subject. In his universe, humanity initially settled the stars in ram-scoop ships flying star-to-star at near-c velocities. Later, the advent of hyper-c drives allowed man to traverse interstellar distances in days rather than years. However, the two could not easily interact.
A ram-ship harvested the free fuel floating in space to reach terrific - but sublight - speeds. A hyper-c ship exited the Einsteinian universe to do its bit; when it returned, it returned with its former ant-speed momentum. It never went to near-c speeds because it never needed to - the hyper-c drive got it where it needed to go, the sublight drives got it the rest of the way. Finding a way to rescue the crew of a ram-ship using a hyper-c ship was a real challenge; it involved first finding a way to accelerate the hyper-c ship to the ram's speed, then using the hyper-c drive to get out there, rescue the crew and return, then finding a way to slow it down afterward.
I meander a bit. Point is, ships in Traveller do not travel at near-c for a simple reason: they've never needed to. My scout's 0.01c and a bit more seems possible, implied in the oldest canon material: a Book-2 chart showing a 2g ship taking 117.9 hours to do a thrust out 900 million miles to a far gas giant. My own research suggests there might be some dangers, but nothing devastating - provided of course there's someone on hand to rescue you if an unlucky roll takes out your power plant. Beyond that is uncharted territory - here there be dragons. There are a few mentions of races going interstellar by sub-c methods, but no details. Other than that, throughout canon - and be cautioned that I've laid eyes on less than half the canon material out there and probably remember only half of what I've laid eyes on - ships simply use their drives to get where they're going: from jump point to planet, from planet to jump point, sometimes to a gas giant or some interesting anomaly.
Thus, to infer a limiting factor because it hasn't been done - well, maybe, but then again maybe not. Other than maybe the slowboat colonies (and it's not clear how fast they went), there's no mention that anyone's actually tried. Best rule of thumb remains: whatever works for you.