Nothing wrong with making double rifles on shotgun actions if a few simple principles are adhered to. Sadly, in the rush to acquire a cheap double rifle, these principles are being pushed towards the 'back burner'.
OK, the hammer-gun pictured in the first post is a Webley & Scott. This is being tossed up as some kind of rationale for sufficient strength to allow safe conversion. I couldn't find any reference to the donor guns' proof, but they all look like black powder guns to me. (the Husky is Lefacheau(sp)-opened, for goodness sake!). Even if nitro proved, they are likely to be proved as game-guns rather than pigeon-guns, and even though the W&S has a Greener cross-bolt, I wouldn't have chosen it as a donor for a nitro rifle conversion over other options.
The 'rules' for selecting a shotgun action used to be:
heavy nitro proof (European heavy proof, or UK pigeon or waterfowl proof) NOT game-gun proof;
No BP proof under any circumstances;
Third fastener, preferably Greener cross-bolt;
Generally robust features, eg heavy gun with long action bar, wide breech, etc.
Of course, if the gun is properly proved with the new barrels and load, all should be well, but without delving through every page on the Ruppelt website, I couldn't see anything obvious about proof. Buyer beware.
Don't get me wrong: personally, I reckon converted shotguns are marvellous things, having owned, shot, and hunted with a converted Greener 'Empire' in .577 Light Nitro for many years now, as most of you know. Here's a link to the original story of my experiences with that gun for the new-comers:
Greener .577 story and a couple of hunting stories:
hunting story _
another hunting story