It's Animation Cancelling, if you do a Shot, an Attack, and then jump during the Attack Animation, then you are able to shoot again immediately after the jump. It can't be done in the air, IIRC, so you have to wait until you land to cancel the Attack, but thankfully the timing works out perfectly so you can do this to get one shot on the Ground at the start and cancel it to get one in the air, then another shot in the air on the way down, that you then cancel with this tech again.

The button sequence is R1> wait until the bullet spawns, then Square, and at least one frame has to come out of the attack before doing Cross and R1 to cancel it and shoot again. Do that again on the way down, and just keep repeating that loop

Nyoom

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