I dont think the 223 improved is much better then a 223 rem for me to go and have my barrel swapped but if thats what you want then go for it, what I can tell you is a inexpensive way to make brass for your 223 improved, Take some factory loaded 223 rem and fire form it in the 223 improved chamber, the 223 rem cases will take shape to the exact dimensions of the 223 improved. Thats how two of my friends make brass for there 223 improved rifles.