The only real reason to convert to the 209 primer is if you plan on using pellets instead of loose powder. The 209 was added to make the pellet ignition more reliable. It is actually not such a good idea with loose powder as the original standard 209 primers were too hot for most loose powder and caused crud rings and other problems. Now they make "special" lower power 209 primers to try to fix that problem. It is much simpler to just use loose powder and stay with the #11 primers (RWS primers preferred). When all is said and done spending the extra for the conversion does not make sense to me as I think pellets are not the best way to develop a real accurate and reliable hunting load. Again this is just one persons opinion. The 209 might be slightly more weather proof but that is not set in stone either. Many say they have no problem with #11 primers in bad weather.