Tom, this guy makes really, really good bullets and has always been very reliable and fast. Unfortunately success has allowed him to get more expensive as well, but it's still nothing like jacketed bullets.

http://www.proshootpro.com/

There are other sources on the net if you look a little. If you find one and aren't sure about them...ASK. Some places are slow as molasses and some are little more than scams.

I would suggest you start with the PR45-300G bullet. This is a 300 grain bullet but I think you'll fall in love with it and be amazed what it can do in your rifle. It's only $47/250 bullets. And it is a gas checked bullet, which I would highly recommend. He has a good 400 gr. gas checked bullet available but the price goes up fast. No since paying that just to get to know your rifle. Frankly, I doubt you will ever want anything larger than 300 gr.

PS - I've talked to him on the phone a few times in the past and he's not an unreasonable fellow. You might talk him into selling you something of a "starter pack" consisting of a dozen or so of two or more bullet styles to help you find which one works best in your gun. Frankly, I think I would order them in size .459 rather than .458. This is no big deal in cast bullets but often aids accuracy considerably.