I'm not sure why a faster twist would not work with lighter bullets, unless the RPM and velocity tore up flimsy jackets. Ballistic Tips will not do this. I do not think you can load a .223 hot enough to "shred" a 40 gr BT in any normal barrel. They are designed to withstand high RPMs.
I have had a Savage .223 with a 1 in 9" barrel for at least 15 years and have shot many, many sub-half inch groups with 40 gr V-Maxs, Ballistic Tips and 50 gr Speer TNTs, BTs and V-Maxs.
I just got back from Arizona a couple weeks ago and shot a couple hundred 40 gr BTs with great results for me. Not so great for the prairie dogs, though.
