I think the breech-loader referred to in the Needham advert is his needle-fire, shown on the 4th page of this thread. Needle-fires were apparently around from the 1840s onwards.
I've just been reading that military interest in the needle-fire by the Prussians, Austrians and Danes did not go unnoticed in British military circles (and to those interested in foreign affairs), something which might have facilitated the later acceptance of breech-loading sporting arms to some extent.
I've examined a needle-fire rook rifle, but I've never held a needle-fire game gun.
I'm also still pondering the horizontal pinfire that AaronN mentioned. I've never seen one of those either.
I'm starting to realize that one lifetime is not long enough to study sporting arms.
