Shot like a dream. Noticeably low recoil, and muzzle rise. I would say that my R51 it is not much easier to rack the slide on than my other autos (colt 1911.45 cal and CZ-999 .40 cal).
All rounds that fired had bulged primers, didn't seem to effect functionality. I thought all the issues I had were ammo related (I shot nothing but dirt cheap ammo, all eastern bloc; except the Blazer). about halfway through shooting I decided to keep one round of each ammo type, and there was one FTE so Actually shot 246 rounds.
I shot the following:
49 rnds Hot shot (Steel) – 1 Failure to Ignite, light primer strike, but the primer felt recessed.
50 rnds Tulammo (Steel) – No issues
49 rnds ZVS (Brass)– 6 FTE
49 rnds Blazer Brass – No issues
49 rnds Wolf (Steel) – No Issues
So I search the web quickly today and found Military Arms Channel review and decided that it may have been more than just the craptastic ammo:
https://www.youtube.com/watch?v=aTzS4sQfn4U
MAC had a bulged case just like RyeOnHam (youtube user name of another R51 owner). I didn't have any bulged cases, nor did a shot fire while partially out of battery. The fire arm returned to battery after ever shot with the exception of possibly the failure to ignite.
Reference photos attached to see a photo of the FTE. It looks exactly what MAC called a "double feed" I think. In my case it was certainly a spent case that did not eject.