what would be a good size for a 223?
say out to 500yrds?
Dave

I presume you are shooting small targets.
I have a leupold 6-18x on one and a Leupold 6.5x20 on the other. Mine are used for prairie dogs. Most of the time I run them at about 16x when shooting PDs.

I also have 6.5x20's on my 223's.

4x16 should be plenty. While it sounds good, when you get to high on the magnification you run into haze and mirage.

First, let's get the nomenclature right, guys. A 6-18x would be a scope with a high lowest power; a 6.5x20 or 4x16 would be something with very small objective lens.

On the OP, a 4-16x42 would give a power low enough for close-up critters and marginal utility for 500 yards (almost twice the range normally assigned to the 223 Rem) without too much bulk for a smallish rifle.