The key mechanical features always "work" but little stuff like "gun fails to cycle 500% more often with the particular spec of ammo a particular force uses".

The key mechanical features always "work" but little stuff like "gun fails to cycle 500% more often with the particular spec of ammo a particular force uses". A rifle spec'd out for sale to Cambodia probably is going to have a lot of teething issues if you try and sell it to the Swedes unchanged. Are these things "safe"? IDK. But no force is going to put in an order for tens of thousands of guns unless correctable issues like those are proven fixed. Infantry arms are a battle of margins. Everything "works" but a marginally more finicky gun to use is going to mean the people using it are marginally less effective which extrapolates pretty directly to "safety". At the end of the day the analogy isn't great and we're building a castle in a swamp here.