To throw a wrench in things... my first AR was a 20" RRA Predator Pursuit. It is a tack driver and the rifles and complete uppers can often be found for cheap, particularly the older ones with slick FF tubes or other not-so-tactical features. They come with 1:8 air gauged 223 wylde barrels made by Wilson. Mine does pretty well 55gr ammo though it seems happiest with 62gr.
A gas gun probably will not be as accurate as a bolt rifle and may be a little pricier... but with a soft shooting round like .223, shooting a semi auto through a scope is pretty fun. No need to break your cheekweld/grip to throw the bolt so follow up shots are fast.
Otherwise I was considering a Howa 20" varmint 223 bolt gun once upon a time. They have a 1:9 twist barrel iirc. Worth looking into.