refreash my memory, should i use the reg win209 or a cci209m or fed209m? the reason i ask is i had 3 hangfires the other day with reg win209.

i may have been due to a dirty plug. i was using what i thought was the same load as last year but my groups were no where near as good. it got me trying different bullets. i had been using 120gr of bh209 and 250gr barnes tez.

what would make a difference in my accuracy? dirty plug? worn out plug? how would you tell if the plug is worn, approx how many shots in the lifespan of a plug?