I don't know if it's a big issue, but I believe that at least some commercial S&B .223 ammos has steel-jacketed bullets (possibly with a copper wash or something). I checked some I had and it was the only .223 that attracted a magnet (to the bullet). PMP, PMC, Winchester, etc. didn't do this. This was 55 grain ammo. I don't really know if this is a problem (I'd be interested in hearing more informed opinions on this) but it's something to consider.
Doug