Definitely have your training partners use gloves or something if the shirt is even close to tight, and if you aren't small for your weight a size 50 will be reasonably tight. Concentrate on getting the armpit of the shirt set in the middle of your own armpit.
If you have it set back more towards your lats it will cut and hurt even more than it normally does. Also, make sure that the arms and armpit are set in the right place after the shirt is pulled down over your head but before you try to pull it down over your lats. The lats should be the tightest part of the shirt, at least in my experience, so take your time and get it set evenly and with no slack as it gets pulled over your lats, otherwise you may have to take it off and put it on again if you screw up.
Another note, I personally found that the way of "jacking" the shirt in a blast shirt pulling the front neck up , as opposed to down as you would with most current generation shirts. So to get more out of the shirt pull the back and sides down, but not the front, while to make it easier pull the sides and front down.
Belting the shirt will make benching a lot less painful and give you a bit more from the shirt as well.
My first shirt was a 46 blast shirt from a smaller 181 lifter when I was 210lbs and 50" across the shoulders, so don't worry; the shirt will break in with time and it won't be as tight or painful. Given the size you should be able to get it on and set right within your first couple of sessions. I also managed to get 70lbs out of the 46. It will never be as comfortable, as easy to put on or give as much carryover as a soft back shirt, but you won't have the problems of needing ridiculous weight to touch or a shirt that refuses to let you bench with the technique you prefer.