I had a conversation with my Russian-speaking friend and he used this phrase to describe his impressions of the newly purchased rifle. "Я тут паре типов своих показал его. Они выпали с аппарата." I barely understand that he show the rifle, but the other part is complete mystery to me. Is this some slang gibberish? What the meaning of this phrase?
It's slang all right, but it's not gibberish. Without seeing the context, it can be roughly translated something like
I showed it to a couple of my mates. They were totally stumped.
(Note that I am using showed it, as you mentioned a rifle in there).
Word тип, apart from its main meaning type, kind is also used to refer to a person, usually in a somewhat derogatory manner, and usually a man, e.g. подозрительный тип could be translated as twitchy bloke (although word-for-word means suspicious man).
Выпасть с аппарата is one of a large number of slang phrases meaning to be totally stumped. Some other ones you may encounter are выпасть в осадок, офигеть и т д.
I'd like to add a bit to Aleks G words.
Выпали с аппарата I consider as
they were impressed much by the rifle. Here
c stands for
из того, что собой представляет or
от вида (механизма)
Please nothe that the first person boasted of the rifle, so I expect there really is something impressive, and the impression is stressed by the word
Выпали which is quite rarely used alone.
"Я тут паре типов своих показал его. Они выпали с аппарата."
As far as I understand, the OP author understands the first sentence (though barely). Just in case I will still explain it: In this context "типы" - means "guys", "своих" means that the speaker knew them before. "Тут" rather means "recently" than "here".
The second sentence is more interesting. It looks like it is a new kind of slang. "Аппарат" in this context means "летательный аппарат", so the literal meaning of the phrase is that "they fell down from the plane". "Аппарат" on the pilot's slang meant "plane" since long time ago. See here for example, in the end of "Жаргонные фразы" section. In 2009 there was a stunning news that in Omsk region one of pilots of a glider used for agricultural spraying fell down from the plane when the plane was 300 meters above the ground. Here we can see that newspapers use jargon words ("аппарат") as if they were common use. The news was discussed on internet quite a lot and in person I guess, too. So, most likely it was then when it entered the youth's slang. The meaning of the internet discussion is that it is hardly possible to fall down from the glider because there are a lot of safety features. Pilots do not fall from the plane normally.
When the phrase entered the slang it changed its meaning from literal to figurative. Something like: "they were so amazed that totally lost control and fell from the plane".