I have always assumed that except for length a 222 a 223 and a 5.6x 50 were the same.
Not so according to Wiki.
The base of a 222 at 376", a 223 375" and a 5.6x50 378".
Because of where I live 5.6x50R cases are pretty rare and when 100 once fired cases came up on the internet for a very reasonable price I bought them. 
Full length resized them and they didn't want to eject when fired in my little BSA Martini.
Checked the base of the case of some S and B factory rounds and they came out at 373". The RWS I had bought were 374".
With a fine file I carefully filed the base of the case down from 374" down to 373" and low and behold now no problems with ejecting.
Next job is to check my 222 and 223  cases to see any variations in the base of these cases that occasionally don't want to eject in my little Martini's.