This is an old post but thought that I would report the ultimate solution to my initial question. OU812 suggested the Forester St line seater which don't know why I never thought of them as I have had one for a 40X Rem. 25-06 for many years. Another moment, I guess.
Ordered one for the 6mmx223 and it arrived yesterday, special order. It was the answer. Without going into a long boring tribe, It solved several problems that I was facing while loading, which was basically at a stand still, for that Contender 6mm. Works perfectly. And, was exactly what was needed.
Just illustrates that some times, simple suggestions can also produce desired results.