Cast bullets don't do well above 1200 fps.
With gas checks, proper sizing and loading, 2000fps is easily obtainable. And accurate.
Use a 180-200 gas checked bullet of medium hardness (WWs or harder) and sized to .310", over 34 grns of IMR4064, either of the 4895s, or Varget. Safe, accurate, and no leading in the bore or cylinder. I've shot around a thousand of these through my Garand, and abour 600 similar loads through my M1A with zero problems.