![Image](http://www.ranchdogoutdoors.com/Firearms/RG4570/images/SAAMI_4570_chamber.jpg)
The rifle is timed to accept a 2.550" cartridge, it just cannot chamber a heavy cast bullet because of the case bulge. I ordered the Pacific Tool .458 Uni-Throater with a 3° taper. This is a pretty cool hand tool, over a plain Jane throat taper reamer, in that it allows you to establish the current cut and then move forward in .0005" increments while examining the cartridge chambering between each increment. Once you have the cut where you want it, the length can be locked so it is repeatable with the same model of firearm. Only thing that needs to come out is the bolt and extractor and you cut it with hand pressure.
This rifle continues to impress me with my daily testing but I want to be able to shoot my 300, 350, and 425-grain bullets at a 2.550" so I did something today that will start taking care of just that.