Agreed, no oil on the hop-up or in the barrel. Also, try not to run the cleaning cloth, patch, whatever through the hop-up itself or you may tear the rubber.
Remove your barrel grouping and look down the barrel, if there is even dust/debris a gentle wipe or two will suffice. If for whatever reason that's not enough, a drop of Windex or two.
WE'RE RECRUITING MORE AGE VERIFIERS FOR MORE REGIONS OF CANADA! INTERESTED? CHECK OUT OUR THREAD HERE!
BC & YUKON MASTER AV REPRESENTITIVE