I like the RPR, I got one for my wife in 6.5 CM, and my son just picked up one in 308.
Personally my go to long range target rifle is a Model 70 Target Rifle in 308.
The 6.5 CM is an excellent long range rounds.
But lets not get carried away, its not about the rifle, or cartridge, long range shooting is about fundamentals and the ability to "weaponize math".
You have to take into account weather, humidity, elevation, wind, temp., angles, etc.
Anyone or combination of the above can cause you to muff the shot.
Range finders are great, if you get the right one and set it up properly.
I use the BR7. If you set it up right, to 1400 yards it will take in most of the above environmental concerns. Just range the targets, it gives you the "come ups" and to a point, the adjustments for wind.
But it all goes out the window without good proper fundamentals.
As to the PRR (and other target rifles) being heavy, that is an advantage.
Follow through is critical. We have a tendency to relax as the hammer falls. This causes movement of the rifle, and since it takes more effort to move a heavy object then a light one, the weight of the RPR is important.
For example, as mentioned my wife has a RPR and I have a Ruger American Predator, both in 6.5 CM. Using the same ammo they shoot the same place, the Predator is just as accurate. But its harder to shoot unless you have a good solid RELAXED, position. When totally relaxed, and the hammer falls, and you relax, you don't disturb the rifle because you have already in the place where you would naturally fall when the hammer falls.
As to heavy hunting rifles. There are basically two ways to hunt. Stalking and Glassing. I use to run through the woods (when I was younger) stalking, trying to be super quiet etc. Now I'm old, I don't run anywhere. So I set and glass. I'll set all day in one spot, far enough from where I would see the critters without disturbing them. I can also smoke, and fire up my little gas stove and make coffee. I'm far enough away the critters arnt spooked so I have time to set up.
I've found out I see a lot more animals, and I also found that a heavy rifle is not a disadvantage. But this is also where my BR7 comes in. It gives me confidence to judge distance and conditions and make any necessary corrections to my zero.
The RPR in 6.5 CM (with proper bullets) is excellent for this type of hunting.
But like anything else, it takes lots of work. I dabble in precision rifle shooting. I have a place I can shoot in excess of 2000 yards. I set up my steel 8 inch target, load up on my 4-wheeler and drive all over the range, stopping here and there to engage the target at unk. ranges, angles, wind directions etc.
I enjoy this as much as hunting. Not being in the mountains, but the hunting itself. Heavy rifles aren't a disadvantage here either.