Again, historical it was not an improvised weapon, it is called gunstock by what it looked like, not what is was moded from. Besides, every club under the club listing is a improvised weapon, this was not. It was designed to be a weapon and was effective too.
I'm sure it was effective. It looks functionally similar to the armour piercing axes used in the middle ages, which whilst they did less damage against an unarmoured opponent than a broad bladed axe were far better at piercing armour. Being made of wood it would have less penetrating power than them.
I think for me the question is, is the player going to be using it as a traditional weapon as used by their people for generations, as pictured, or are they wanting a modern, high tech shadowrun weapon. If the latter, I'd be pretty happy with the initial suggested stats, if the former, I'd proabably drop the accuracy and AP a point, the availability a bit, and the cost a lot.