decided to ditch the optics mount from HKParts.net. it still needs some minor grinding out of the bottom rear side. its not a complete flush fit out of the box, which is what it was advertised to be. i have opted for a G&G L.P.M for G3/MP5 Series Low Profile Mount. order placed today, ive heard good reviews.
other than that the weapon runs fine, eats anything you put into it, only about 10-15 hang ups in 800 rounds so far. not bad for a semi auto magazine fed rimfire in my opinion. the front sight post likes to loosen up and become a big wobbly after a good string of shooting, bolt may have to be touched up with loc-tite.
still my new favorite plinker, if you dont have one yet, youre wrong! (or theyre sold out)