One man's experience:

Back in the 60's I had a lot of correspondence with John Buhmiller, who may be a familiar name to the older crowd. John killed over 100 elephants and countless buffalo after he retired from gunsmithing at age 70 or so. Anyway, it turned out that we had been thinking on the same lines about a .50 bolt action which would approximate the .500 NE.

What we had arrived at independently was to shorten the .460 Weatherby case to 2.500" (so it would fit in the magazine of a standard action), neck it to .500 and use 570 grain Kynoch .510" bullets. 90 grains of 4064 produced 2150 fps in a 22" barrel. I used a P-14 Enfield action, which holds 3 in the magazine and one "up the spout". With it, I have killed three elephant, six Cape Buffalo and one black rhinoceros (Rowland Ward). The whole rig, with Lyman 48 rear sight, weighs 8 3/4 pounds, which means quite a bit of recoil, but makes it great to carry with all the walking involved in elephant hunting. I never noticed the recoil shooting at game.

One of the great pleasures of shooting this gun has been the countless rounds of cast bullets I have put through it. It was a constant companion on walks in the woods, where any number of shots at tree stumps, rocks, targets of opportunity in general made me thoroughly familiar with the sights, the safety and "catching aim" (as Colonel Whelen would say). This came in handy when faced with a charging rhino, who had circled back and came totally unexpectedly from behind. Three quick shots put him down in a hurry.

Going this route is really "on the cheap", but it has produced a totally reliable rifle upon which I would not hesitate to stake my life again, if the situation called for it. Keith Francis made the reamers years ago, but I would think any reputable reamer maker could duplicate them from a fired case, which I would be happy to furnish, if so desired.