Yes, some people have noticed that monolithics do expand more reliably and, probably, wider when fired in a faster twist. Our friend Dwayne (BC30cal) from British Columbia has noticed the difference in how TSX's act from the fast twist in the 6.5x55 versus the slower twist in the .270 Winchester. In fact, partly because of this he discovered his .270 has a slightly slower twist than the standard 1-10. (This isn't all that unusual, especially in older rifles. Before button-rifling and hammer-forging became the industry standards, sine-bar cut-rifling machines were the primary method used by factories. The rifling they cut is adjustable, and quite a few barrels had somewhat oddball twists. One of the several older .250-3000 Savage 99's I've owned had a 1-15 twist, as I discovered after failing to get 100-grain Speer Hot-Cors to shoot in the rifle, a bullet that normally shoots fine in a 1-14 twist.)
Twist has an even more noticeable effect on lead-cored bullet expansion. The most extreme example I've seen occurred a couple years ago, when Nosler first introduced the Varmageddon bullets. I was shooting prairie dogs with the head of their rifle division, and he was shooting their new AR-15, made by the late John Noveske, with a 1-8 twist barrel, using the Nosler factory load with the 55-grain tipped Varmageddon at 3100 fps.
I brought several rifles to the shoot, but started with a tang-safety Ruger 77 in .220 Swift, which of course had the standard 1-14 twist. I'd handloaded the same tipped 55-grain bullet to 3800 fps.
Guess what? The .223 "sploded" (a West Virginia term) PD's noticeably more violently than the Swift. This didn't happen just once, but consistently, on many dogs, throughout the day, out to 300+ yards.
