Some thoughts on this:
I believe the lumps on those DRs went through the bottom of the action because of the larger hinge pins H&H used to withstand the extreme pressures and energy those guns generated.
The way it was explained to me was that a bigger pin means a bigger lump which means more surface area to displace the energy generated by these rifles. Without these enlarged surfaces, these rifles would have gone off the face very quickly.
If the maker wanted to keep the lumps enclosed, they would have been forced to use a bigger action. This would have increased the gun's weight and ruined some of its sleek, aesthetic appeal.
I don't know why lumps-through-actions went out of favor on shotguns at the end of the 19th century. But just like flat-back actions and back-action locks, they did. Probably because they looked old timey.
Once builders like Purdey set the standard for the Best and received Royal approval, everyone else had to follow.
I was also told that the front lump on Webley & Scott 700s goes through because of an oversized hinge pin, too. The maker used an oversized pin because the hinge pin on these guns is fixed and it cannot be replaced to put the gun back on the face.
Something else: if guns with through-lumps are harder to make, why did makers keep using them on their low-priced guns? I think it's because the hole lets them machine the hinge-pin in place - a cost-saving measure that is a sign of a low-grade gun.
BTW: has anyone ever seen as final-version H&H Royal shotgun with a lump coming through the bottom of the action? I don't think I have.
OWD
