I have an R51. It has the Pedersen delayed blowback action with an internal hammer, no trigger safety.
I have shot 150 rds, 100 115gr UMC and 50 124gr UMC, FMJ.
I had one failure very early on, the first time I tried 7+1 the 2nd round FTF. Since then the gun has been perfect in function. I could have made an error in topping off the mag when it failed, 7+1 has worked every time since.
It is easy to rack the slide.
The three dot sights are good. For me, the sights are regulated low with 115 gr., slightly low with 124 gr. In any case, for self defense purposes it's close enough with either.
Trigger is crisp and I would say moderately heavy. The grip safety takes a definite squeeze to make the gun hot. Both features IMO are desirable for a single action CCW.
I have put 3 shot into an elongated hole at 10 yds freehand, and shot proportionate groups at 25 yds. I can't ask for better performance from a compact autoloader.
Fit and finish are very good for the purpose, the internal surfaces are well finished.
Now field strip and assembly, I watched the videos and read the manual, and I still had a steep learning curve getting this thing apart and back together. After a few times doing it I got it down to minutes instead of fractions of a hour but it will never be Glock easy. Barrel has conventional rifling. Expect it would shoot cast fine.
I bought an R51 because I wanted a 9mm (first one) and I was bored with tilting barrel actions. Very satisfied with it and will shortly get a carry holster.
Would recommend to a friend? Yes