You will not and should not see a 50 BMG with a weight of under 40 lbs without some type of muzzle brake simply from a safety stand point. Held properly tothe shoulder and with a shooter properly trained to shoot a 50 BMG, even a 25 lb 50 BMG would not break bones butt it would not be all that much fun to shoot.
To the untrained shooter, it could be dangerous but likely more to the face and forhead then to the shoulder.
I have shot my 510 Allen Magnum (50 BMG improved) with custom 835 gr SPRBBTs to 2900 fps without a muzzle brake. This rifle was on an AR-50 with a heavier barrel contour, finish weight was roughly 35 lbs. IT was NOT FUN to shoot but it was not dangerous simply because I was very well trained at shooting the big rifles. With a 5 port muzzle brake I machined for the rifle, recoil was very managable.
If you look at the Barrett semi-auto rifles, their recoil is extremely comfortable for a 50 BMG class weapon but that is because there is alot of energy absorded in making that semi-auto system to function and the very aggressive muzzle brake also helps alot. Recoil is less them most 12 guage pump shotguns.
Now as to velocity of the 50 BMG. Most load data you see is out of a 45" M2 barrel length. In my experience, you will see around 2600 to 2650 fps with the 750 gr A-Max with comfortable loads. Chamber pressure can be checked by rechambering freshly fired cases. The fired case should rechamber with little to no effort to close the bolt on the fired case. If the bolt is hard to close on a 50 BMG case, your pushing pressure to hard.
It is an easy thing to push the 50 BMG to over 2700 fps with the 750 gr bullet and some rifles will do this with relatively mild pressures. I had an LAR Grizzly with 36" barrel that would do this easily but my 31" AR-50 will top out at around 2650 fps with same loads.
You also have to be careful about load data. Hodgdon lists 233 grains of H-50BMG for the 750 gr A-Max. In most single shot rifles with quality chambers, this load will lock up a bolt solid on a fired round. Most rifles will top out in the 210 to 215 gr range with this powder. If your bolt lift is sticky on a 50 BMG, YOUR WAY TO HIGH IN CHAMBER PRESSURE.
Point being, we will mostly be shooting the 50 BMG in quality single shot rifles, not the loose chambered M2 so start low and work up and pay attention to pressure. The 50 BMG does not work on high muzzle velocity. IT works because you throw a HUGE bullet with extreme BC to moderate velocities. Do not try to muscle the big 50, there is no need and in the end it will bite you back!!!