Mine seem's to like dirty..I clean it real nice, scrub for copper deposit, oil it,,then dry well before shooting with denatured alchohol swabs,,but then it takes about 8-10 rounds before it dials into moa again.
I got mine used,,unknown round count,, took about 150 rnds of various bullet weights before I found it likes 40grn v-max and/or 40grn Nosler partition types at around 3000-3200 fps,,there isn't a dealer within 60 miles that has WWB, so darn it,,I've been forced to buy loading equipment, now maybe I can step up in weight a bit and tune the loads for it.