Kinda wide open, with lots of variables. Bottom line is how accurately you can shoot, combined with your restraint to pass up marginal shots. Deer are so gosh darned easy to kill with the right shot, yet pack lead with the wrong shot.
Power-wise I've killed a whole lot of deer with a whole lot of different handgun cartridges. Frankly your 50 cal RB probably has as much poop as the 45 Colt and 44 Special standard velocity loads I used (240-250 grain bullet @ 750fps MV), with consistent one-shot kills out to 54 yards. But I sure passed up a lot of shots, too.
I'm betting that if you can get the MV of that 175 grain RB up in the 1000fps range (do-able with 40 grains of 3f Goex, according to the Lyman manual), a well placed shot will do the job out approaching 50 yards. After all, when guys kill deer past 100 yards with a 50 cal rifle the ball velocities are similar.
Whether pistol or longer ranges with rifles though, it's down to the shooter's skill and judgment.