Sorry to say that tac foley knows less about any Holland & Holland combination gun than he does about underwater cake-making for the deaf.
In general, from what little experience I have regarding Holland & Holland, just making an observation that people who buy a $100K gun usually have people who supply the ammunition.
I suppose I could call them up and see what, if anything, they might recommend...
'kay. Just done it. I'll post any resplone.
BTW, here is a note about about 14g - true, he is talking about a shotgun, but.....
John Clements
UK
This 14 bore round action, Damascus, doubled barrelled hammer gun is owned by John Clements. It was bought a few years ago and brought back to life by the acquisition of a box of 14 bore Eley Gastight cartridges. It would appear that 14 bore cartridges stopped being manufactured in around 1920, which may explain the excellent condition of this gun, but also makes firing it difficult. There have been several suggestions that various continental manufacturers are still making limited quantities of 14 bore cartridges but as yet I have not found them.
I obtained a quantity of 14 bore brass cases but unbeknown to me 14 bore cartridges where made in two sizes of rim, either thick or thin. Unluckily the gun is thin rim and the cartridges were thick but luckily this way round they could be machined down. They do work but have a habit of being difficult to extract. I have loaded the gastightes several times but the best way I have found to shoot the gun is to use conventional 16 bore cartridges and wrap a couple of layers of masking tape round the case to create a snug fit. This works extremely well and she kills pheasant as well as the best of them when I point her in the right direction. While she has been nitro proofed I tend to load the old gastights with black powder which work really effectively with 28gm of No 5’s.
The gun has recently been converted to take 16 bore cartridges by the fitting of chamber sleeves to take the slightly small cartridge. This is a reversible process as the sleeves are only glued in place and no material has been taken away from the chambers.
Sadly, you would probably like to shoot it with ball, in which case, as we say over here, you are stuffed. Pending, of course more useful advic(s)e from Messrs Holland & Holland.