"if the hammerless boxlock had come first"
It did. The patent for the Anson-Deeley hammerless action dates from 1875, the Beesley action used by Purdey from 1880, the Round Action from 1881, and the Holland Royal was later still.
The Boxlock is the the older action, it is the watershed that shifted SXS design from lever cocking to barrel cocking, the principle on which all other "great" guns are based. All other SXS owe a lot to the lowly Boxlock.
The Round Action in my opinion is the best looking SXS ever built, but there is more to it than aesthetics. It combines the desired 90 degree sear to tumbler engagement, a solid bar, intercepting safeties in a package that is more compact than a sidelock.
Stocking is sensitive point in guns with grip screws. Stock bolted round actions, like the modern Chapuis prove that stocking can be as strong as any other double gun. The Chapuis can be counted a true round action as it has a trigger plate lock and rounded bar.
Um, the boxlock really didn't come first-the hammerless sidelock is a hammer gun with the hammers inside. They, hammer guns, that is, were in full bloom well before the boxlock. The hammerless Beesley action is several modifications and enhancements to a hammer gun, nothing more, or less.
Generalizations are dangerous territory when speaking about double guns. See below.
A Darne is lever cocked (after a fashion, at any rate) and not "barrel cocked".
I find them to be great guns. If they owe anything to the lowly boxlock, I don't know what that would be.
I love examining and shouldering RA guns, but, honestly, every one I've ever seen was quite old, a bit creaky, and very expensive. Not sure the care and feeding of one would be my cup of tea, regardless of all the advantages the design allegedly offers. I feel the same way about a lot of old sidelocks, however.
Had one, that was a money pit. I don't, anymore.
Best,
Ted
