My 550 came in today with a 223 conversion kit. I mounted it to the bench and started to put it together. The directions were very good I thought. I had a little trouble with the shell plate. I tried to adjust it without a case. I put a case in a turned it half way between station 1 and 2, snugged it down and it works great. It comes with the large primer system installed so I had to change it over to small. Very easy I thought and didn't take very long. The powder measure came with the small powder bar installed and I need the large. It was also very easy to change over. I did learn that you have to keep a close eye on the little square white plastic thingy. I have the powder die and measure set height wise but not the charge. I did not install the rest of the dies yet. Overall I am very impressed how easy it was to set up. It seems that it should also be very easy to change calibers but I do see where it would be an advantage to buy extra powder measures with the conversion.