I've heard that before, but as much as Bill Ruger over-designed his guns, I don't think he would consider putting a 10mm into a P89 sized pistol. He definitely upscaled the P89 to make the P90 (chambered in .45ACP) and while he boasted that the P90 would handle the 10mm, he made at least one comment during an interview implying that he wasn't much of a fan of the 10mm and never intended to chamber a pistol in that caliber.This platform was originally designed with the 10mm in mind...