Well Chigurrh has the mannerisms of a jedi you basically can't have emotions since everything leads to the dark side. So we know he will have no qualms in holding back. It comes down to his attack and defense and style of fighting. Palpatine has his powers and I feel having an airgun only slows Chigurth down in fast sequence duels. However, if his m.o was to be clearly a Jedi sniper than he have more of a chance. But Palpatine is too damn powerful especially with Neon Moon particles flowing in him.