Hi,
My neighbour has a combination gun in this rifle calibre and having done all the comparisons the .223 Rem reloading dies appear to be good to use as all the dimensions except for the length of case below the shoulder are the same. The neck on .223 is 0.203" and on 5.6x50 is 0.266 so being longer should work for the neck sizing. The difference in length of the case below a .223 is only 0.147".
The dies for 5.6x50 are too expensive for the few times they would be used by me for him.
I have a sketch of all the dimensions but I cannot see a way to add this image to the post.
