I have a Remington Model 700 (was an ADL but now has a detachable magazine) in .300 RUM I noticed first that the primer shows a much deeper hit from the firing pin than I have ever seen with my other rifles or pistols. It actually has a raised lip around the dimple that is fairly substantial. In addition at the very end of the neck it has a groove after being fired that is about 1/16th of an inch wide going all the way around the casing with the exception of 4 very small interruptions in this groove at North, South, East, West locations when looking straight on. The rifle shoots great, the rounds cycle through just fine. But I am not sure that I could trim these casings up for reloading. As an additional note, these are all factory loads so far. I have put less than 40 rounds through it at this point. Thoughts? Not sure where to begin and I don't yet have a gunsmith here in Eugene. I currently use a man out of Olympia, Wa but that is a long distance to go.