The main causes of incompatibility were the transition from ball-and-powder to rimfire cartridges, then the transition from rimfire to centerfire. It's surprising how little firearms have changed in the past century. 9mm Parabellum is 125 years old. The Browning short recoil action (used by most handguns today) is over a century old.
[–] toyg 2 days ago
[–] ggreer 2 days ago
Most improvements have been in things like modularity, sighting systems, and standardization for mounting accessories such as lights and laser aiming modules. Better metallurgy does mean that modern firearms tend to last longer than older ones, but even a firearm from WWI can fire thousands of rounds before the bore erodes enough to hurt accuracy. I doubt we'll see any significant change in small arms unless something revolutionary comes along, such as portable energy weapons or mass drivers.
Isn't that a function of constraints in the deployment model, which are fundamentally unchanged? A soldier needs <something> with him to hit enemies and <something else> to reload it - and the simpler the better, to facilitate difficult deployments and keep costs down. I mean, the venerable Kalashnikov is still around, despite its well-known shortcomings...
I guess we would see major developments only if we discovered/engineered materials that can perform the function in a significantly better way.