If you want big bore in an AR15 package, there is also the 450 Bushmaster and 458 SOCOM to consider. Either of those might do what you are looking to achieve without having to make a one-off rifle. Of course if that's what you want to do, then I will not say don't pursue your dream.
As others have said, keep it lubed and shoot it. It appears to have improved as you shot it. If it still does it after a couple hundred rounds, then I would look at what else may be happening.
With possible exception of a RR LAR-8, this should work well.
https://www.larue.com/products/tacops-1-sniper-for-ar10/
If you buy it and it doesn't work, I will buy it from you for what you paid, including shipping to you and to me if needed.