I purchased a Patriot Ordinance Factory Revolution Di 12.5" 308 Pistol. I did a form 1 to a SBR. When I removed the brace and tried to install an MFT minimalist stock I could not get it to fit? I originally purchased the stock for an AR15 but had a leftover so I thought i could install it on the POF buffer tube but it did not fit. Any suggestions/insights would be appreciated