The guy is obviously a habitual or pathological liar. There is a difference in the two. A habitual liar lies to make themselves look good. They know they are doing it, and keep doing it in order to give the appearance of importance or knowledge. A pathological liar really does not know they are doing it and the things they say seem to make sense to them. They have a very loose grasp on reality. We have alll known people of both types. Either one is extremely irritating to us honest folks. Their stories always are the best, biggest, etc.. With a habitual liar, you can usually call them on it and they will either shut up or go on about how you don't know what you are talking about. They will never be able to prove what they say, so they will have to ridicule the challenge. With the path. they are usually good people with a decent attitude, and you can usually guide them in the right direction. They generally have no idea as to the truth, and are not being arrogant azzes like the bs'er.
As I write this, the thought occurs to me that you will generally only find the habitual liar on forums like this. The pathological liar does not seem to post much on these type of things. Probably because they are not looking for "glory". The habitual liar will always look for venues such as this, mainly because they can stay relatively anonymous with very little chance of being called on their lies face to face.
There is not much you can do with the idiot of which you are referring. The best defense to him is to become very knowledgable on the subject of firearms and shooting. This will give you credibility to others and the ability to prove him wrong immediately.In the long run, it may help curb his bs at least when you are around. Probably your best bet in the short term is to call him on being shot. No scar, no wound, period. The only tissue in the human body that does not produce scar tissue is the tongue. everything else, including the brain, will scar.
It is possible to trim his feathers a bit, it kind of depends on whether it is worth the effort for you. Keep us informed on his stories, they sound like a hoot.