It's pretty easy to rack up sniper kills on the right map. I think my record is in the twenties, and I'm a pretty terrible sniper, I just happened to get on a custom map where I could cover all the entrances from my position and I was the first one out of the gate. 51 is still pretty impressive though.
My most kills is 17 (Demoman on Dustbowl Section 2:Cap 2), but my highest score is 38 as a Medic. It's amazing how many assists you can rack up when you are healing red team on Dustbowl Section 3:Cap 1.
i think my most points, has been as a sniper. I had either 17 or 19....
I can imagine a sniper getting 51, if you are good enough, well positioned, and always get HEAD SHOTS!!! haha, couldn't resist. as a sniper you get a lot of assists since you miss the head a lot.
The moist points I've had in one life was when I played on the 3rd stage of Dustbowl as a spy. I had 20 points ALL in backstabs... I don't think I'll ever be able to do that again...lol