With a reddot I can get some decent sub 3 inch groups at 50m
with my factory built RRA 7.5" LAR-15 Pistol in .223
it's a light fast-to-target AR and I never have any reliability issues with it. I don't get the 'Loud' complaint people have. Loud is relative. No louder that a 12 guage

.
Get one with a proper buttstock. Using just a buffer tube is a bit of a joke.
As far as ballistics go, paper doesn't care about fragmentation.
And as far as economy goes with relation to 9mm. You can't convert 9mm to shoot
.22lr.
Get the .223 shorty of you want.