Sowerbutt's Shooter

Sowerbutt pushed the barrel of his shooter into McGaskie’s cheek. “Why should I believe a word of your nonsense, McGaskie? You promise this, you promise that. I need information.” His hand connected with McGaskie’s face with a loud smack. 

http://www.amazon.co.uk/Colour-Smoke-London-Sowerbutt-Novels-ebook-x/dp/B00RYR8BWG