Ugh, in an effort to reduce the charging effort, I removed the cocking tube support, polished it some and attempted to install an extended charging handle I got from hkparts.net, which I think is wrong (not for a "K" model). Once installed, it was a little difficult to pull back but when I did, it did not want to go forward. I had to tap it pretty hard and in turn, marred up the slot the handle rides in. Keep in mind, without the pin installed, the handle move forward and back easily and I know the pin was centered when I pulled back. Any suggestions for a fix? Should I just take a file and knock the edge off and put some black touch up paint? Ugh, I'm such a dumbass.