For a $4k budget, you are seriously into a couple of suppressed pistols. A Browning Buckmark in 22lr with a Silencerco Sparrow, and a Springfield 1911 in 45ACP with a 45 Osprey.
For any range less than 600, there's no need for a 50BMG. Plus, with the more reasonable cost of 22lr and 45ACP compared to 50BMG, I'll bet you'll get a lot more use out of two suppressed pistols than on 50BMG.