I just think it's safer to take advantage of Remington's replacement offer and get a properly made version. As I said, I want to like the gun, it's ergos are great, so I really see little downside other than the wait.
I don't think barnbwt is suggesting you not do that. But he is an engineer and likes to try and understand how and why things work of don't. I'm kind of that way myself. Both of us have seen a lot of wild misinformation based on wild speculation as to what is happening inside the R51. A lot of this is due to people who think the R51 works like any other locked breech semi auot they are used to. But it doesn't and this causes a lot of confusion.
With a Browning tilting barrel type system, such as the 1911, the pistor is in battery when the barrel lugs and slide lugs are fully engaged and this occures when the slide is fully closed with the boltface in cotact with the barrel. In the R51, the pistol is in batters when the breech block drops in place in front of the farme lug. At this point, the slide may not be fully closed and the even if it is, the breechblock can be almost 0.10" from the barrel.
This "play" in the breechblock is necessary for the Pederson action to cycle, and is safe, but looks very much like an unsafe out of battery condition to anyone who does not understand why it is there. For many, the explanation just convinces them the gun is unsafe.
As barn says, Remingonton ammo has deeply set bullets with no shank extending past the case mouth. This ammo will fully chamber in all weights I have fired, 115, 124 and 147. American Eagle, for one example, is not seated as deeply and about .05" of shank extends past the case mouth on most rounds. These rounds engrave on the lands when the bullet is seated. and may not allow the slide to fully closes, depending on how well the pistol is lubed and how may rounds have run thorough it.
When I first started shooting my R51, only Remington ammo would chamber reliably. After 500 rounds, it will take ammo that used to cause no ends of problems. The bullets still engrave on the lands, but as the action has smoothed up with use, there is less resistance to the slide closing from anything else, and the slide seems able to overcome the bullet resistance on the lands.
I now have problems causing my R51 to fail. This is a good thing. Once I see what ROC has done with the new production gins to address the first run problems, I will decide whether or not so send mine back. They may not do anything to the chamber. After all, it causes no problems with Remington ammo and the manual clearly states that use of any ammo other than Remington and Barnes may void the warranty. But if they don't do anything to the chambers leade, I may just keep what I have.