I have fire formed factory loads, and loads of fast pistol powders to Vols in the 2000 fps range with out loosing brass. However, there is an odd factor regarding K's and that is the reamer used, as there are many slight differences in shoulders. A friend of mine can not fire his loads in my rifle, but I can fire his loads just fine in mine. The gunsmith who K'd my rifle said that the reamer he used was the original Lyle Kilborne specs.