M37s made with serial #855,000 (1963) and higher have interchangeable barrels. Your friends "87" was made in Kings Ferry. That Ithaca regime made some good ones and bad ones, but any issues can easily be resolved. The gun is mechanically simple and has barely more parts than an anvil. The Upper Sandusky folks are tops and can resolve any parts issue your buddy may have. The earlier guns were capable of "slam firing", but the Kings Ferry and Upper Sandusky won't.