Well pooch if you are talking about the Purdey I do believe that there is some forty plus years between the two the gun is Victorian the Titanic was Edwardian. Also the Steel plate and rivets used in the Titanic where not of the Quality recommended by the ships designers. In fact it was an inferior more brittle grade used due to pressure from the ships owners the White Star Line to keep costs down so the bean counters got their way again. Now when it comes to ship engineering Harland & Wolff where second to none they put the ship together correctly given the cash restraints they where working under, though Purdey had no restraints at all they used the very best of everything that includes the steel Iron and Engineering hence the guns longevity.
And as for the quality of materials and Engineering painting blame with a large brush is rather unwise. Lets see was it the materials poor engineering or cost cutting that caused the shuttle "Challenger" unpleasantness not so long ago. The materials and engineering from that age are all around us today.
