Re: 223 Remington vs 5.56x45mm reloading help
Aside from what has been said already, and to help clarify it; There were 2 different 5.56 loads and a 223 load. The 2 5.56 cases are the same, but loading data is different for the M193 and the SS109 rounds due to the 1 in 12 twist for the original 193 and the 223 and the 1 in 7 twist of the SS109. The main difference in the cases is that the 5.56 brass is thicker, and so uses less powder to create the same pressures. So if you're loading 223 brass, you can certainly use 5.56 loading data and work up from there for hotter loads. But if you're loading 5.56 brass, using 223 data will create too hot of a load to begin with. Stick with the data for the 5.56 to begin loading that brass. Also, check the gun you're going to use them in to see what the rifling twist is, and start with the proper loads for that twist no matter which cases you are loading. In short, to be safe, always start with the lowest charge or weakest load, then work up for what is safe in your gun. What's safe in one may not be safe in another. Know your gun and match your loads to it. This takes trial and error, or advise from someone else loading for the same gun is always a great help. Cartridges of The World is a good reference (it gives you all of the measurements you'll need) to give you some factory and hand loading data that has been tested, and there are many other good reference books for hand loading available also.
Last edited by OldFotoMan; 02-29-2012 at 02:24 PM..