Double Rifle
My dream rifle is a double rifle as well, and I own seven double rifles, and have owned many more over the years. My favorite double rifle is one I no longer own. It was an Army & Navy 450/400 NE 3". As many of you know A&N didn't make rifles but was sort of like the US miltary PX. It only sells things other make but with their name on it. The double rifles they sell may have been made by any of the English makers. Mine was made on a very good Webley action, and the rifle was most likely made by Westley Richards.
The one thing I can tell you is the 505 GIBBS is not the best choice for a double rifle,being a rimless cartridge, and of fairly high chamber pressure, it is not well suited to a double rifle action. Though it is a fine cartridge a better choise would be a 500NE 3" , with it's lower chamber pressure, and flanged case. The 505 GIBS requires a true magnum action, and a true Mauser Magnum action is a very expensive action, anf hard to come by.
The double rifle new or old are simply 19th century technology, and not well suited to high pressures. All the NE cartridges are fairly low pressure cartridges, toping out at around 45,000 CUP, and most in the 10,000 to 15,000 cup range. The flanged case helps with extraction, because the extractors can be made quite massive, while the extractors for rimless cartridges, use a small retractable pall, that is spring loaded and retracts into the extractor body then pops back up into the rimless extractor cut in the case. These little palls are suseptable to breakage, espacially with high pressure cartridges, and are also suseptable to jamming in the down possition, because of dust, a comodity that Africa has in spades.
A proper double rifle that is to be used for dangerous game should be made with very high quality irons sights, a non-outomatic safety, chambered for a rimmed (FLANGED) cartridge, of low pressure, double triggers, and made to fit the person shooting it, or an off the rack rifle that fits the owner properly. The rifle needs to be ballanced with 1/3rd of the weight between the hands. Selective ejectors or extractors is a matter of choice.
A proper bolt action rifle made to be used on dangerous game shoutld first off be a CRF (controled feed) action, push feeds need not apply, and should be fitted with quality iron sights, and if scoped should be fitted with quality quick detach rings and bases, so the scope can be removed and replaced so that it returns to absolute zero every time. The safety should lock the fireing pin not just the trigger. Any bolt rifle that is to be used to save your bacon should be 100% reliable and feed, and eject "EVERY TIME" with out fail! The bolt rifle can be made to use very high chamber pressure cartridges, and rimless, or belted rimless cartridges, and the finished rifle needs top be made by a man who understands DGRS (dangerous game rifles). No rifle of any kind should be taken out of the factory box at taken into the field with dangerous game with out a real DGR smith going over it to smooth out the ripples in the feeding.
Bolt or double rifle, the weakest part of the rifle is the nut pulling the trigger, and since the owner is the one at risk if it doesn't work properly, the time, and money spent makeing the rifle right, needs to be equaled by the amount of time the owner uses learning to shoot the thing properly!