Hi GB,
I have been using the Barnes X bullets in my 15 444 Encore barrel because I have been getting jacket separation with everything else I have tried. The Barnes bullets really work great in it and I am pushing them with 55gr of 1680, which gives me fantastic FPS. I was just wondering how they would work moving in the low teens? They probably wouldnt have enough velocity to open up and create the proper shock wave that they are intended for, as you have suggested.