You might wanna look at when the cl_hook_activeweapon runs and put the +fire there. Might need +fire ; wait ; -fire but that might block input for one frame. defer might avoid that but some servers intentionally break it. There's also nextframe. Or just learn to release manually.
I think you acc will suffer though - you need to be aiming at target at the point it fires but you're not in control when it fires. Wouldn't be more logical to invert it and first fire, THEN switch away? This would mean you have 9 fire buttons though if you have 9 weapon binds.
<packer> when i see martin-t's name my blood pressure increases
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[BOT]Hоtdоg> anyone here lives near martin?
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[BOT]Hоtdоg> will pay monies for shooting him