We ran just about 5,000 rounds through an early R9 test gun, pre-prefix serial number job, and the issue at around the 5,000 round mark was the right hand side of the frame, where the barrel pin goes through, developed a slight crack. We closed the tolerances between the frame and the trigger sear bar by .030" and made the frame area where the barrel pin goes through on the right side a full enclosure of 360 degrees, giving strength to that bearing surface. Issue resolved. To note those frames, we added the "R" prefix, designating that updated stronger frame. The "R" prefix meant two things: "R" for revised frame and "R" for Rohrbaugh. So, while those 47 or so early no-prefix guns are rare, they also are not as strong as a prefix R9 model. Now if you "Carry is a lot and Shoot it a little". . . . . you should be just fine with that early R9. My early gun is still in service 14 years later without frame cracking in that discussed area. So there you go. . . . another behind the scenes bit of information for the "R" within the serial number of the Rohrbaugh R9 pistols. That is the meaning of the change in numbering.
As you cane see, as with the outer recoil spring, the bearing surfaces of the frames. . . . we were constantly upgrading trying to make our pistol the best we could. . . . . and I believe we did a good job in that process. ;-)
Regards,
Eric R.