Depends on who you talk to and what shamanic culture you are referring to. On a broad level, the journey is similar. Both are journeys of the soul through what many believe to be its native dimension, the astral plane. However, the main difference is that most often astral projection occurs through deep meditation or dreaming while shamanic journeys are induced by drugs. Hope this helps.
While traditionally shamanic journeys had been induced by the use of drugs, they’re generally frowned upon by modern shamanic practitioners. The shamanic state is contemporarily induced by a low-theta beat (about 4 cycles per second), which “entrains” the brain to pulse at that same rhythm. This brain state has been primarily associated with heightened visualisation.
Deep meditation is not required for shamanic journeys. In fact, it’s generally encouraged to avoid deep meditation in favour of the more shallow variety so the shamanist can keep “a foot in both worlds” – to remain in the physical and shamanic planes simultaneously.
As for the difference between the two, I have not experienced a state that I could attribute to what others describe as “astral”. Based on what I’ve encountered through literature, however, the astral and shamanic states differ in that the astral body actually separates from the physical body and the shamanic body is more of an “extension” that remains connected to the overall body still “attached” to the physical body.
Shamanism is highly subjective as it relies on, from what I understand, the brain’s (and perhaps body)’s ability to entangle itself with local and remote environments, as with remote viewing. The data received are then converted by the brain into concepts for the conscious processor to interpret.
Perhaps someone with more experience in both shamanic and astral work could elucidate further.
To me, they are very similar, but are also different in some ways. There is much more control and will involved with pure projection vs a drug induced one, at least for me. To me the drug induced journey is alot more distorted and uncontrolled. Although alot can be discovered through the induced journey, a whole lot more will be learned by doing it naturally. Also it seems that our full being is not included during a trip compared to a natural one. For a member of a tribe to do it is more of thier way of life and they have different experiences from a sacred ritual compared to a person living a modern life does. They live closer to nature than we do, every day, and it makes a difference also.