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I cannot comprehend how or why any hunter or target shooter would ever put down a loaded firearm
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You mean with the safety off, right? An unloaded handgun is useless.
I had much slowness getting here, hope that doesn’t keep up!
When waterfowl hunting, the gun is always loaded, and rarely held by the hunter. In a boat, the only choice is to lay it down (as apposed to leaning it against something, it might fall and go off....).
Field blinds often are nothing more than a pit with 1 foot of water in the bottom, laying the gun on the berm is the only choice.
It is safer to lay a loaded gun down than to get into a tree stand (though, not by much).