Most rigid Boyd's stock style ?

[foxx]

^^^^^ that's about the nicest I've ever seen.

[Rosco]

Have a Pro Varmint and Varmint Thumbhole both are very rigid and I think either would be fine for a .223 Sporter or even a bull barrel. The Pro Varmint has a 26'' Heavy Varmint barrel and the thumbhole is coupled with a 24'' Light Varmint barrel and I don't have any problems out of either.