Heavy varmint contour in krg bravo chassis

I run a 26 in. HV contour and no issue.
Your shorter barrel would balance even better.
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At 21 inches it will probably balance okay. My Whiskey 3 can get front heavy with big barrels. You won't find a more solid system for the money in a Bravo.
 
I'm running a 26" McGowan #8. Plenty of clearance. Balance isn't horrible, but I did add about 3lbs of shot to the back to balance once I added the 1lb can on the front.