Looks like free-floating the barrel did the trick. It was 26 degrees at the range this morning with no wind. The cold weather really helped cool my barrel and I was able to shoot much faster. I used my IR temp sensor to monitor the barrel temps throughout the shooting session. My best group came from a load of 44gr. of IMR-4064 topped with a Hornady 140gr. SST. I'm getting 1/2" groups at 100 yards! (see pic below)

I also couldn't resist bringing the newest toy to the party, my Smith & Wesson M&P-15.
It's now shooting 2-1/2" groups (or better) at 100 yds with a battle-sight!