On the topic of the RXM, I think it's very compelling at least conceptually. For what it's worth Gun Talk Media ran over 8,500 rounds over two days, with Glock factory and MagPul magazines, through their copy without stoppages or parts breakages. It shouldn't have parts breakages at that round count, but it's good to see the lack of stoppages. They don't show the full firing of the gun from start to finish, so they could have faked their results, but I'm going to choose to believe them.
I've read about a couple issues that some users and reviewers have with reliability due to either their screws for their optic being too long or over torquing screws in their optic inducing malfunctions. You will impede on a spring that is visible through the drilled out screw hole. This is possible and somewhat common to happen with a factory slide that you have milled. It's also an issue with optics cut P80 builds/other clones. Not exactly an inherent fault with the gun.
I've seen reports of the slide stop causing issues, the ejector being out of spec, and the same complaints echoed above about the magazine issues. What's real or user induced will come out in time. About half the complaints I've seen have been user induced from guntubers and a good amount of real issues seem to be fixed by swapping a part for a new Glock OEM part. I'd echo again what was said above, don't buy the first gen, Ruger will iron out the problems eventually. Lots of shilling by guntubers though, hard to find higher round counts and clear videos of why stoppages occur.
