I wonder about this caliber. What cases�do they use for it?
Who offer reloading dies?
What velocity?

Kalle

Karl-Erik , the 458 RCBS is made from the 45 basic case. I use the ons sold by HDS, probably made for them by MAST (Bell). In your post to me you ask about the difference between this cartridge and the 450NE 3.25" They are two intirely different cartridges. The 458 RCBS is easily rechambered in a 45-70 No1, because it is a simple matter of lengthening the chamber to accept the 2.75" case of the 458RCBS. No extractor work is needed. I made my chambering reamers out of a 458 Win Mag reamer, and the round can be loaded with a backed off, 45-70 die set. Dies are available from RCBS, but are special order, and it will take about 18 months to get them+ $$$$.
If you have access to a copy of "THE HANDLOADER'S MANUAL OF CARTRIDGE CONVERSIONS" BY John J. Donnelly , the discription of this cartridge is on page 635.
The 458 RCBS has a case capacity of 100.13 grs water, while the 450NE 3.25" has a capacity of 136.04 grs of water. The 458 RCBS has a rim dia of .595" , and the 450NE has a rim of .626". Actually the 450NE 3.25" requires more work to rechamber either the 458 Win Mag or the 45-70. The 458RCBS cannot be rechambered from a 458 Win Mag, without backing the barrel up eqal to the depth of the belt on the Win Mag case, then rework the extractor.
The 450NE 3.25" would be the best of the two, IMO, but if you are starting with a 45-70, I'd rebarrel with a heavier barrel, if starting with a 458 Win Mag, then the 450NE will clean out the old chamber, and the barrel is much heavier, and sights are already fitted. I have an un fired No1 458Win Mag that is headed for a 450NE chambering.