Thread: 17HMR barrel cleaning

My father has owed a 17hmr for a about 2 years. I use it on the odd occasion. It's had a brick of ammo through it in that time (250 rounds?). It's never had the barrel cleaned, and we have both noticed its accuracy has dropped off a little (50 metre zero seems fine).

Given its skinny little barrel, what equipment do I need? How often should it be cleaned?