Update:

Installed the night sights; really no change in POI.  Have from the beginning used the "center" or "combat" hold and still too low (7-10 yards).  Mostly shooting 115 grain bullets not +P.  Expect to try 147 grain again and see if any difference now that I am more comfortable with the gun.

Total of 425 rounds down range, two cleanings to date.  Shot 75 rounds last night and only one nose dive using S&B FMC.  Have found that the mags work better if when fully loaded you rap them smartly on a flat surface to seat all rounds back into the mag housing.  Both IMI and S&B JHPs shot very well, no issues at all. 
Trigger still a little gritty/jumpy, but then I prefer a SA revolver over an auto loader anyway.

My gun (see my other post for serial # range) has Remington Arms Co.  Huntsville, AL       R51 all in a line starting almost to the far back of the frame in a single row.  Serial # is to the right and below.  The hash box (I hate these) is directly above the grip screw.
FYI

Bought R51 @ local gun show on 9/8/18.  Serial # H0066xx91R51.  $290 NIB no tax, no fees, no transfers, one hour background wait only due to gunshow traffic.  Thought I would give it to the GF for a carry arm after I test it and break it in.

300 rounds down range so far.  Yellow box UMC's and steel cased Winchesters (both 115 grain FMC) are the best so far with really no problems.  Tula steel case are NG!!  Speer 124 grain FMC are hotter and had issues while the Remington green box 147 grain and the Fiocchi 115 grain (both FMC) are just OK.

Nose dives seem to happen because of the shape/length of the bullet.  Speers and Tula are longer and tapered while the UMC and Winchester are shorter and rounder.  Next up are JHP bullets which I think I will favor Remington and Winchester.  Have some S&B 115 grain so they will go first.

All loads shoot low with a center POA.  Have a Trijicon set of sights I will install to see if the POI will move up any.  Great looking gun, nice feel and hold but just a little disappointed in the POI/POA.  The fussiness of the ammo is not a huge issue (yet) as long as we can narrow it down to a couple of loads that work well.  Mags so far don't seem to be the issue.

From NH, just got the gun at a local gunshow.
Like the fit and feel and the fact that it is all metal.
But it does shoot low even with a POA centered on the bull.
Thanks