Is there an advantage to using 5.56 brass as opposed to .223 brass? The reason I'm asking is I'm thinking of buying 1000 rounds of either Olympic or LC855PD just to blast away to get the brass. I know both of those don't have the best reputation for quality of rounds but I just want the brass. Am I better served by getting the 5.56 brass? If not I may just buy some once fired brass for my reloads.

I believe 5.56 brass is a little thicker.  Dont buy anything olympic.

Try Midway USA for Grade 1 once- fired brass. Pretty cheap and has been cleaned, de-primed and primer pockets reamed. Just be sure to sort it for bad cases, something that must be done anytime you are prepping brass for loading. It will need to be sized but it's a good idea to size even new brass.

river_rat,
I was looking at the Midway once fired grade one but I was thinking I might want to get brass from a single lot by buying loaded ammo. I'm kind of an accuracy finatic. I like to know if I miss it was my fault and not from any miniscule reloading factor. My reloads will all be ballistic tips, partitions, or possibly v-max. Although for the price those 64gr winchester bullets are appealing. I like a load that will handle... uh larger varmints if needed he

Quoted: Is there an advantage to using 5.56 brass as opposed to .223 brass? The reason I'm asking is I'm thinking of buying 1000 rounds of either Olympic or LC855PD just to blast away to get the brass. I know both of those don't have the best reputation for quality of rounds but I just want the brass. Am I better served by getting the 5.56 brass? If not I may just buy some once fired brass for my reloads.

Brass is brass