Interesting topic which made me review my PMs from Oct 2010 with a German friend about creating a 0.510” 505 Gibbs which would fit in an H&H length action (COAL 3.6”) DGR.
Didn’t make up a rifle for it but originally considered either a CZ Magnum or Ruger RSM, with a preference for the latter because of the feasibility of reboring a 416 Rigby (heavy barrel) or 458 Lott to .500”/.510”. I made up several dummies with Barnes 570 gn 0.509” monolithic solids. Looking back now, a Win M-70 long action, restocked for a larger magazine assembly which would allow at least 3 cartridges in the box, would better fulfill the original intent - fitting the modified 510/505 Nu Gibbs in a standard LA easily available DGR.
Altering the case to fit the COAL with that bullet required shortening the neck, but the Gibbs case retains at least the capacity of the 500 Jeffery case, so that cartridge’s MV should be achievable.
The main issue for this project is magazine capacity in the RSM or Win M-70 LA, which would favor the CZ Magnum route, but would negate the original intent. I still have the dummy cartridges and will post pics if I can figure out how. May need to revive the project later in the year. Too many irons in the fire currently.
Last edited by Wildcatter264; 04/13/23. Reason: Spelling errors, added info
