That Mountain Rifle has a smaller diameter barrel than the regular Remington barrels, that's why it weighs less....Free floating a thin barrel like that is really taking a chance, it might be worse, those thinner barrels usually need a pressure point to shoot well....

It sounds like you haven't spent a lot of time with load development, I'd work on that before I start free floating....

That barrel is going to get warm quick, it's just the nature of the beast, I'd shoot twice and let it cool...Actually 1 1/2 inch groups from a rifle like that is acceptable....If you continue shooting once the barrel gets hot you will open up the groups, it's not the rifle's fault at that point...

I'd just check all the mounting screws to the barrel and scope, give the barrel a good cleaning and start your load development.