Re: how many rounds before shooting for groups
I broke-in my Howa 1500 as I Audette Ladder Tested.
Breaking-in the barrel doesn't make it more accurate; it causes the barrel to foul less, so you need not clean it as often to keep what accuracy you have.
Like liltank said, you're going to have to either develop a load or find the ammo that shoots well in that particular rifle.
"If you love wealth more than liberty, the tranquility of servitude better than the animating contest of freedom, depart from us in peace. We ask not your counsel nor your arms. Crouch down and lick the hand that feeds you. May your chains rest lightly upon you and may posterity forget that you were our countrymen."-- Samuel Adams