Id like to get an extra barrel for my 300 rum or possible 30/338 lapua. I see some different bore and groove dimensions avail for 308 barrels. What the recomendation for bullets in the 168-190gr, 3 groove,4, 5,6 groove??? I see a bore listed from brux of .308 and .298 and am thinking it could be beneficial for the big mangum cratridges erosion. I guess the norm is .308 and .300. I dont know if it would be beneficial to go to a smaller groove diam?