I think it depends on the type of piercing and how open your hole is. But I highly recommend bottoms search for pierced tops to use you. It increases your chances of anal tearing and direct exposure to the top's seed.
Ive been fucked by a pierced poz top with a nice thick dick. I don't open up very easily, so that metal had to push into my sphincter and I could definitely feel it scraping me, probably if you open up easily it won't make as much difference because there isn't as much pressure/friction.
It was an overnight fuck. He kept using me, roughing up my hole with his piercing. The first load was a normal hot fuck. When he started fucking me the second time, after a couple minutes he pulled out again and showed me his dick. It was streaked with pink. I growled like a beast, could not believe how much it turned me on to be getting a REAL breeding. He put a white towel under my hips so we could see how bad it got. Then I told him to plunge it back in and do what we both knew we wanted. It hurt going back in but we were so crazed it didn't matter. He came in me four times, and by the end that towel had red spots all over it from the juices dripping out of me. The adrenaline rush of letting a positive man ejaculate in my roughed up hole over and over was so intense, I got a buzz as strong as if I'd chugged a six pack of beer.
So go find a pierced top and let him do bad things to your hole. You'll love it.
Rmemeber, kids: "if it bleeds, it breeds."