I've got a Beowulf on a DPMS lower and have had zero problems shooting 325-400 grain bullets through it. For me it's about a 125 yard gun, after that trajectory starts falling off and with the Propoint on I just don't want to start having to hold over. Out to 125 though it will roll over the deer and pigs. think of it as a 45-70 in an AR platform. Mine shoots one big ragged hole at 100 yards with the 400 gr. factory load.
I also have a 6 x45 upper that Marty at Teppu Jutsu built for me, I've just started load development but it looks like it wants to be a one hole gun. I shot several loads Tuesday in crossing winds 20 mph gusting to 29 mph and even with that it wasn't bad at all. Hoping for a few windless days to really get a preferred load worked out.