@Bill - which one came first the hen or the egg? You can build your load for your gun, or you can (within limits of standard pressure etc.) build you gun for you load. There isn't any differencen in having your new double regulated over you own ammunition - if the ammo is out of the box the has the stamp Norma, Hornady, Federal or Handmade of Maximus have absolutly no difference for the gunmaker!

@Maximus - personatly I wouldn't care for making exotic ammunition for a 500 NE. The cartdriges mades is repurtation from "woodleigh" like bullets. If I had the oppotunity to have at double buildt I would have it regulated with Kynoch. I could allways then use my sparetime - or long winther evenings - to dublicate the regulation load by handloading. But since you would like some more modern bullets for your gun, I still would make the ammunition that the gun should be regulated with myself.