The comments about the M60 machine gun above highlights the fact that machine guns in particular do need to be durable. Whether or not there are stamped parts is beside the point and, anyway, stamped parts are really a heavy industrial kind of thing to produce, at least as far as machine guns go. But they do have to last. You can't have small arms (or other arms either) that quickly break down or wear out or are finicky in service. Some machine guns incorporated oilers for the ammo, which I can only imagine increases the critical nature of the functioning. But I'm sure the designers thought just the opposite.
The biggest differences between a military weapon and a sporting weapon are that the military weapon will (hopefully) be more robust and will have a better rust and corrosion-resistant finish. Only recently have hunting rifles been availabe that are really weather proof. If you see old weapons in museums, it is true they had better finishes than later weapons but it didn't contribute to their functionality one bit.
Shoot low, sheriff. They're riding Shetlands!
Underneath the starry flag, civilize 'em with a Krag,
and return us to our own beloved homes!
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