It has nothing to do with mag on non mag. I don't like the regular CCIs either. They come out dirty. When a primer comes out dirty its brutally obvious all the energy from the primer is NOT going to the powder.

Its called head space (for lack of a better term) and the Win209 simply fits better and has been 100% reliable for me in no less than 12 bottle of BH209 and roughly 7 DISC based NFPJ based Knight rifles.

I cant see any reason to use a mag primer in a Knight/Lehigh NFPJ plug unless they fit better than a Win209 which to this day i havent seen one that does.

My ULA is just the opposite, it uses CCIs. Either the mag or non mag. A Win209 is just too long to close the bolt. There is really nothing "special" about it as you preferred to call it. They are just designed using a different primer.

Lehigh probably chose to use the Win209 just because it was the longest and you would have the least amount of problems if a primer was on the long side. Crushing a primer too far could even be hazardous.

Im very surprised someone who has been around on the forums so long needs this level of explanation considering its been gone over at length numerous times.