Not really in firearm design since the 1950s/60s or so. There are small improvements, but the basic operating mechanisms everyone's using haven't changed since

Not really in firearm design since the 1950s/60s or so. There are small improvements, but the basic operating mechanisms everyone's using haven't changed since then. (Compared to the previous 60-70 years which saw the introduction of smokeless powder, box magazines, self-loading, automatic fire, etc.). (Optics are seeing this kind of development though).