I have paperwork sent in for a .308 Winchester monocore suppressor with a total length of 9.5". I was thinking of building an AR chambered in .300 Blackout to go with the suppressor; however, I want to minimize the rifle's length and put in an SBR barrel with an endcap and the suppressor body attached to avoid the additional $200 tax. What would be the best way to affix the endcap and body to the barrel? I am planning to put the suppressor markings on the monocore's endcap so I can build another body and endcap to use on a couple of my other rifles.