I am a VERY CRITICAL examiner of my castings. If they aren't eyeball-perfect, back they go. I don't let gas checks "Cover a power of sins", either (to paraphrase Mark Twain). If they aren't right, then otra vez.
I have yet to venture into the 30 caliber plain-based realm. I have played in 25, 31, 36, 38, 44, and 45 caliber rifles with plain-based castings, with fair success and considerable enjoyment. 1050-1350 FPS has been the usual velocity range for me, the trans-sonic buffeting occurs but it is variable and somewhat unpredictable. Shorter, lighter flatnoses are less-affected than are longer, heavier ones IME. The 38/55, 44/40, and 45/70 have done extremely well with slugs started at 1100 FPS.