Just buy the High Energy .243 rounds.

assuming a long action, taking a thread off the barrel and setting the shoulder of the shank back the same amount will allow the 240 Wby reamer to clean up the 243 chamber with no problem. - Dann

Well, I could be wrong in this, but here's how I see it. yes the 243 case is wider at the base and at the shoulder, however; (Hercule Poirot pauses dramatically, finger twirling his heavily waxed moustaches), the 240 Wby's belt is wider, and once you've shortened the barrel and shank one thread (which should take the chamber inwards at least 1/10 of an inch, right?), the belt area in the new chamber should clear up the base area and the first 0.10" or so of the 243 chamber. As well, the 243 shoulder is wider then the 240's but that's at a shorther distance into the chamber then the Wby's shoulder. In other words, where you measure the 243 is NOT where you measure the 240 (1.8043" vs. 1.9920, respectively). So you can see where I would think that a set back should be enough to clean up the chamber. I don't have both of these cases handy to measure the differance at the various points of the two cases, so I'm going by Howell's drawings, but it certainly looks doable to me. FWIW - Dan

Chic's right......I just checked my own books. You will end up with a mess if you try that. I would recommend the 6/284. I have a 6.5/284 and I enjoy it thoroughly.