I'm shooting from a portable shooting bench, bi-pod on rifle and small bag in the rear.

PMC is okay ammo, but I would not use it to benchmark a new rifle or optic. A few inches of spread with PMC would not surprise me. Besides, 147 grain through a 1:10 twist barrel is on the low side for optimal stabilization. I only use my hand loads, FGMM or Hornady match when bench marking new equipment.

Verify that your action and lug are centered and action screws are properly torqued. Same goes for your scope mount and rings. If you have a know good/accurate scope, use it.

Lastly, remember all barrels and rifles shoot a little different. I'm breaking in my 10FLCP-K different than I would a match SS barrel. Since it's chrome moly, I'm aggressively cleaning the barrel and have been using a bronze brush up to this point. Plus I've used J-B paste to polish the bore. All of this speeds up the break-in of the barrel. I mention this, because your barrel may not be broke in yet.