I am venturing out of my Glock 9mm and .40 realm and have picked up a Glock 21 .45 acp! Ser. # in the GKWxxx range which I believe puts it around 2004 date. I had read where around this time frame some mod. 21's were having light primer strikes and it was due to a trigger bar problem which was corrected by an upgraded bar---any info on this or anything I should look out for please advise. Love my GLOCKS!! THANKS.