Plasticiser for mortar pointing?

[Wilko]

Hi I am re pointing an old sandstone wall.
I have premix sand,cement and lime mortar mix. Do I need to add plasticiser to the mix for my mortar gun too run smoother?

 

[Dirtmechanic]

Hi I am re pointing an old sandstone wall.
I have premix sand,cement and lime mortar mix. Do I need to add plasticiser to the mix for my mortar gun too run smoother?

They did not use anything like that when they made it. I would not think the result would look original.