This is going to be long winded, so bear with me. The question posted used the word strong which is derived from strength. And it's the strength of every component in a double rifle that matters. So analyzing this more closely we come up with the most important attributes of mechanical devices: reliability and durability. Reliability is the likeliness it will work when called upon. Durability is the likeliness it will wast as long as required. These are depended on materials, design, construction, and maintenance.

Based on the above criteria, most of your English guns will qualify as most have proven the test of time. As far as moder guns are concerned the Searcy and Chapuis seem to be exceptionally stout designs. Some chaps have put 1000's of rounds through these guns without fault.

Lastly, no double rifle will stand up to abuse. If you need a really really rugged rifle – pick yourself up a fiberglass stocked Dakota model 76.