I've made 50 plenty of times. But I also used to mod my gamerscore so my accounts that are 50 have 0 gamerscore. I've been using an account for a few years now and am starting halo 3 again. Normally I'd play normally but it's kinda hard to do without having anyone playing ranked
I doubt you could even find games to get to 50 anymore. I remember I had a guy a year or two ago and I just gave him my gamer tag and my account was a 50 a few hours later. I don't know how he did it though.