If a guy is into reloading and playing around I would suggest a Black Hole Weaponry barrel for the polygonal twist rifling and buy a jar of HBN bullet and bore lube. Im getting some high velocities and safe pressures with off the chart powder loads, 53gr TSX are getting fantastic accuracy and 3330fps from a 16" 223 BHW barrel, I was doing similar tests with 65gr SGK bullets and a whole case max full of compressed Benchmark shooting safely but not chrono and i ran out of bullets. The polygonal twist and the HBN lube keep pressures lower so you can rebuild that pressure with faster burning powder, 65gr bullets act like 50gr, 53gr bullets act like 40s, the burning powder and pressure spike isnt fighting as much friction or resistance to the land and groove rifleing.
My buddy had a BHW 12.5" 6.8 pistol i loaded a quick batch for my buddy and it seemed to act the same way with the tipped TSX, I was compressing the powder charge before pressure signs. My next AR would be a pinned 14.5" or 16" 6.8SPC with a BHW barrel and I would cross my finger that it shot lubed TSX as well and as increase velocity as the 223, I think that would be a nightmare to almost any animal in any woods.
Ive got a now annoyingly long 30" criterion 260AI barrel on a Savage target action and Im not shooting Fclass anymore. Im planning on getting a poly twist BHW barrel around 22" and chamber it for 260AI and see if I can match the 30" barrel on the same action.