In this Military Arms Channel review of the R51, we get to see this interesting new Remington R51 demonstrate a whole lot of problems with a relatively short number of rounds.
A lot of these problems are probably caused by a tight or rough chamber.
A tight or rough chamber can prevent the slide from going into battery completely, which would cause the failures to fire and sometimes allow out-of-battery firing. The stretched case is a pretty solid example of a round fired out of battery. It swelled and locked into the chamber so tight that the slide was unable to cycle, increasing the recoil and failing to eject the spent case and load the next cartridge.
Given that this gun’s recoil operation system begins to cycle the round immediately — the breech is not locked, it starts to travel rearward the instant the round goes off — if it fires even just a little out of battery it will have a lot more case hanging out of the chamber while the gun is still pressurized.
As the number of rounds increases between cleanings, there will also be more powder residue buildup in the front of the chamber. That residue will make the chamber stick even more, making it even more prone to failures to fire, failures to eject and firing out of battery.
If Remington doesn’t figure out some way to address this right away this gun’s reputation will go up in flames.
There are enough people already saying that Remington needs to recall the gun and others who believe that the gun isn’t ready for service. At the very least, it would be wise for Remington to reintroduce the gun and perfect the design with low-pressure cartridges like .380 (21,500 PSI) and .45 (21,000 PSI) ACP before launching a 9mm (35,000 PSI).