After owning and shooting the 338 Spectre, 8.6 blkout 3 twist and 6.5 twist.
The 8.6 3 twist is a dud, and dangerous, limited to low subs and expensive copper only bullets.
With the 6.5 twist, a bolt gun, and hybrid cases its basically a 338 Federal fir supers and better with subs.
No velocity limits of 1000 fps on 350 Makers. I ran them over 1800 fps in the 6.5 twist, no blow ups.
Might as well try the 338 ARC,...but not Hornadys version...something with a faster twist, and maybe just a bit more case capacity like the difference between a 6 Dasher and 6 BR for supers but subs remain about the same, cause the long bullets take up the extra case capacity.
So I did alot of testing with the 338 ARC improved with bullets 160 gr Barnes 2300 fps, 165 Maker 2275 fps, 175 HP 2202 fps, 200 gr Speer 2100 fps, 200 gr SST 2025 fps
250 gr RN 1760 fps, 272 fmj, 300 SMK, 300 ATIP, and 350 Maker, standad bullet 866 fps and 350 gr bore rider over 1200 fps in 6.5 twist 338 ARC improved...200 fps faster than a AR 10, 8.6 blakout with the 3 twist and its 1000 fps speed limit for this bullet.
So here one can shoot a 16" 338 ARC improved 6.5 twist using an AR 15 with no limits on bullet selection or makeup, and hang with the 12" AR 10, 3 twist in 8.6 blackout, ...and shoot jacketed lead much faster with no speed limits.