Personally, I would replace the barrel.
If it is that pitted on the crown, I would think the rest of the barrel is jacked as well.
If you have the tools to change an AR barrel, you have the tools to change the RPR, they use the same tools.
You can buy a pre chambered shaw 10 twist stainless steel barrel for 370 bucks.
They are good quality, OEM type barrels. I have experience with 4 of their barrels, all sub-moa.
No, they aren't as good as a bartlein, mullerworks or krieger, but they tend to shoot very well.