I am on my third 300, the first 2 were dedicated 300 Whisper (prior to the BlackOut), the newest is a 12" blackout upper.
All my shooting is with reloads, various recipes, all subsonic.
The first 2 shot OK, grouped well at times, threw fliers more than I wanted.
The newest 12" SBR (barrel from Spook) in 300BLK, shooting rounds built for my 300Whisper, all reloads are using Whisper dies. The new upper shoots great, much quieter than the 8" upper, much more accurate and reproducible than the 16" or 8" prior 300s. Strangely, the new 300BLK shoots whisper ammo better than any 300 Whisper I have owned/shot.
Maybe one day, there will actually be 300BLK ammo to buy; till then, my gun and I are happy with 220SMK and 209 Amax, both at 1025, both shooting well under 1 MOA at 100 yards.
If you don't like how your Whisper is grouping, consider a BLK barrel swap, it worked great for me.
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