Personally, if I had to blow my head out using a shotgun, I would do it in a very remote location like in a forest where nobody would suspect the gun sound suspicious had someone heard it since there are people hunting in forests regularly so they would most likely attribute the sound of gunshot to someone hunting rather than killing themselves. The blood and exposed flesh would immediately attract scavenger predators in the sky and on the land so most likely the body would be consumed in a matter of 2-3 days at most. After that point if someone stumbles upon the remnants of the body nobody would be able to identify it unless forensic scientists conduct DNA testing or your clothes would be in a condition to be identifiable by your family members. That's why it's a good idea to burn the clothes first and do it naked. Also, I would never take documents or accessories that could be used to identify me.
But, since I'm going to use a very peaceful method not because to avoid my post-mortem body look bizarre but because I want to end it peacefully (I find gunshot method terrifying), I have to do this in my home and leave my dead body there. It's summer now so temperature is high, therefore the body will start decomposing quickly. I think I might not be visited for up to about 4-5 days and that's a long time in the summer for the dead body to significantly decompose to a point of rotting and inflation like a balloon. The skin will look nasty and the smell will be terrible. I just don't give a damn fu*ck about it because I will be gone and (hopefully) not witnessing the scene how they handle my decomposed body but if I witness it somehow, I wouldn't give a fu*ck since I will be broken free from this world and (hopefully) find peace.