No muzzle brake, just a protector bushing. I was thinking 180-ish boolits, and porting the barrel itself with a series of small holes, like 3/32" or even smaller.
I think Mike's rifle is a better candidate for this test because he already has the loads, including one for the barrel before it was cut, so the attempt to restore the original load performance via porting the cut barrel would be positive proof. Of course the harmonic nodes of the short barrel will still be quite a bit different, so the original load may still require tweaking, but perhaps the porting can at least make the slower-burning load more viable.
Gear