I recently sold my K, but I had a similar situation as the endcap I had, had an issue with the swivel coming loose. So I took it apart, went to CanTire and picked up a Fisheye mounting bolt set of about the right diameter, cut down the screw so it wouldn't hit the battery, and just screwed it into the hole. It worked like a charm and I was NEVER worried about the swivel coming loose again.
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Ár skal r?*sa, sá er annars vill
fé eða fjör hafa. Sjaldan liggjandi úlfur
lær um getur né sofandi maður sigur.