Too bad these were not in the same length barrel, but a 20" barrel would be close to what you're shooting the 6.5SS at. My one point on 6.5 PRC is that it would be nice to see a slightly heavier bullet, say, an LRX Bore Rider in the 150-160 grain. Currently the LRX 127 is what most people will use in 6.5 PRC, but it could use a slightly heavier bullet, IMO.
Certainly the 6.5 PRC shooting TTSX 130s will do that. A lot of people taking game at 500-700 yards with it, like Elk and Black Bear. This is one factor that scares me about 6.5 Grendel. I do like it, it's a great cartridge in the mini-action, but going bear hunting with it seems like showing up to the gunfight with a knife. As they say, "shot placement is everything", and I believe if you get close enough and have a well placed shot, it's probably possibly to take down black bears...but it's better suited for deer and pig, IMO. I wouldn't want a 6.5 Grendel with any bear coming at me from 20 yards. I try to work that scenario in my head in case it happens. If it's a Grizzly, I probably want a bazooka...that is if I don't $#!T myself to death...