The barrel coating on my 2016 PCR wore really quickly at the muzzle and ejection port during the first trip to the range. When brand new, I thought it was used because of the coating wear. The coating on my 2020 P-01 hasn't worn nearly as bad and it's been to the range about 10 times.
I think my PCR barrel has a tighter fit which caused more coating wear. (My PCR barrel-bushing play is a lot less than my P-01) So on the PCR, I removed all of the coating by soaking in white vinegar (of course with ends sealed). It came off quite easily and uniformly.