The front sight post will no doubt have the same metric thread pitch on all these carbines. If there is nothing wrong with the cross piece, remove the remnants of the old sight, clean the threads, and reinstall the new one.
If the new sight post is a little loose, back out the new sight until it is almost out, slip a small blade screw driver into the centre slot and prise it apart gently. That will re tension the sight post threading.