A quick note. Speed comes with a cost no matter the chambering. I played nice with my last 25 SAUM barrel and 135gr Berger Hybrids. Chased speed. Never got the barrel hot, strict cleaning regiment. Barrel lasted a handful of rounds past 700. Spendy 700 rounds when you add up the cost of a carbon fiber barrel , muzzle threading, chamber/thread and fit. Barrels are consumables but I prefer a 2K+ round count when it comes to barrel life.
I tried a polygonal barrel on a 6.5-.338 Ultra Mag improved(40 Degree) shot super tight but in the end it was an epic fail. The polygonal couldn't handle 160gr Matrix's bullets @3400 + for long. By the time I worked up a load and got my ballistics app dialed in to my real world. At just over 200 rounds , she was done. Everything went through the target side ways at 300. The weird thing was. When we pulled the barrel and bore scoped it. It wasn't the throat or the led. It was fried for about the last 8" of barrel on a 26" barrel.