There is supposed to be a mag made specifically for the 223 but I don't own it.
I did have to block the inside of the extended mag box to make it work. Alot of fiddling around. Not hard to do but time consuming.
Big issue is the factory top. I had one mag where the lips were not made right and it wouldn't feed well. This one seems to work well.
Jerry
Thanks Jerry!! This helps alot. If I made something up that I could remove then I could still use the extended mag for my other calibers as well. Seems like a good simple fix!