I've ran a few (two boxes of 50, and part of a box of 500) 90gr SMKs thru a .223 Rem - standard A2 NRA Service Rifle legal gun with a Wylde chamber in a 20" 1-7" twist stainless Wilson barrel. IIRC, I was running Varget behind them... rather stout load of 23.5-24.0gr (don't have the load notes available), netted me ~2580-2600fps. Basically... out of a .223 at least, its tough to get them going fast enough to out-fly the 80gr bullets by a meaningful amount.
IIRC, Sierra recommended a 1-6.5" twist, but the consensus was that a 'true' 1-7" would work - mine seemed to.
Still have most of a box of 500 sitting on the shelf that I need to shoot up. Probably won't re-order those; rather I'll stick w/ 75-80gr bullets.
HTH,
Monte
