No i haven't done that! I have seen it done before, Lilja's website had the reamers for it. I am in the process of building a 408 spotter imp. A improved spotter case will hold 200grns of powder, i dont know how well a bbl will hold up to this amount of powder down a 375 bore. If and when some High BC bullets become ava for a 45cal this would be another one for the spotter case. Even a 50cal Amax should be very effective, specially for the california dudes! Below is a pic of a 408 in an improved spotter case, a standard 50cal spotter loaded with a 750Amax and a 50cal BMG round with the same 750Amax bullet. My improved case only features the shoulder angle changed to 35deg and shoulder pushed foward, the case taper was not changed. 50cal Short Mag? almost the same results in a smaller package. I look for the 408 version to be outstanding. I feel the 40cal bullets are the smallest dia for case-powder ratio to bore size that should be used.