I am very particular about cleaning my barrels. With the exception of one time, I have never fired more than 5-10 rnds without thoroughly cleaning any of my barrels. Now, that being said, with this kind of care an maintanance technique, what kind of life could I get out of a nice Hart, Pac-nor, lilja or other high end barrel in 300 UM or UM improved? What difference if any would there be between the life of either the regular or improved version. I know that the standard UM chambering is only about 200fps slower than the 30-378 wthby, which has not the most barrel life, to say the least.