[NAMVET72]

Originally Posted by DrHenley

Commercial 223 brass is marked as such. If it's not marked as 223, assume it is 5.56. Weigh it and compare to the weight of 223 cases to find out whether you need to reduce loads due to thicker brass. My main problem with 5.56 brass is the primer crimp which has to be removed before repriming. I usually give away all the 5.56 brass so I don't have to fool with primer crimp removal.

Originally Posted by MPDC

Col. This may help........

".223 REM / 5.56x45 NATO
.223/5.56x45 Rifle Brass



This is the various selections of all .223/5.56 Once Fired Range brass we have to offer in a variety of quantities and grades. Once Fired .223 Commercial only, 5.56 Lake City, 5.56 Mixes Head-Stamp, Nickel Plated .223/5.56 inventories updated as sorted.

New to .223/5.56 reloading? Check out these small facts that could help determine what type of brass you need:

There are a few things to know about .223 brass but all variations are desirable in their own right. NOTE: Specifications may very by manufacturer, please do your own research on your rifle prior to reloading.

The differences between .223 brass and 5.56x45 (specifically NATO mil-spec) brass is a variation in the thickness of the brass wall as well as the throat length (Leade) of the casing to compensate for higher pressure loads. The 5.56 will have a longer leade than its .223 REM comparable and this is reflected in how both 5.56 and .223 rifles are chambered. Note: 5.56 rounds can only be chambered in rifles designed to shoot 5.56x45 casings. .223 REM ammunition can also be fired through a 5.56 rifle, the small extra space created from the 5.56 Leade chamber will cause a very slight loss in pressure but is not dangerous to fire."

http://www.diamondkbrass.com/.223-5.56-Brass.html

This two hit on the head,