I have been shooting my HK MR.762 for a few years now and loving it!  The adjustable G-28 stock is a must for  precision shooting, very hard to find.  At one point I was trying to buy one though a 3rd party in Europe.  Luckily HK.parts.net come through again and received a shipment of G-28 stocks!  I called up HK.parts and placed an order over the phone Adam stated that the HK 417 / MR 762 have a slightly different recess on the end of the buffer tube.  This was made so the comb height for the stock stayed to the rear when the stock was completely collapsed.  The G-28 stock will fit your HK MR.762 buffer tube with a 5 minute internal mod,  take a look at the pictures its self explanatory.  Overall very happy with HKpart.net and the HK G-28 stock, no more taping crap on my stock to achieve proper comb height.