In reply to:

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You would have only a couple of seconds to shoot. There is just enough time for 2 aimed shots from a double, but only one shot from a bolt.

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Ok then but my choice is still going to be the double.
The only sure stopping of a buff is the brain or spine shot.
Failure to hit either with the one and only shot from the 458 and the odds are high that you could be in for some serious pain.

The fact that with the double you have a second chance if you place your first shot badly, could be what saves your ass!