^^^^^^^^^^^^^^^^^^^^this. Finally someone making sense. Thank you for ^^^^^I don’t understand the reason, but HK installed commercial buffer tubes on the MR223 A3. I found this out the hard way when I purchased an 416 A5 buffer tube from another seller here on the forums. SB Tactical does not make a brace that will fit on a commercial buffer tube. They only fit mil spec tubes. I am sure this is why the original buffer tubes were replaced with the mil spec tube included with the SB Tactical brace. I think everyone would agree including the factory stock when sold as a pistol could be a problem. Including the factory buffer tube may be Ok. However, the commercial tube is useless without a commercial stock which mandates SBR. One could sell it, but that’s it. If only HK would have used mil spec buffer tubes on these guns, the old stock could have been removed, the SB Tactical brace installed, and the factory FDE buffer tube could have been left in place. Enjoy your gun. I for one am jealous!