After an extensive review of available products, my choice came down to Forester Products CoAx Primer Seater or the RCBS Automatic Bench Primer Seater. Both have good and bad points. But, the final selling point was availability. I now have the Forester Products CoAx Primer Seater as it was not back ordered.
As it is a bench mounted tool, I had to find a place for it to sit with limited bench space. My solution was a semi-portable mount. A quick trip to my local industrial salvage discount store that carries a wide range of products. I did find a piece of phonolic material of the ideal size (8x14x1). And, the phonolic material is an insulator that can be drilled and tapped.
The CoAx primer seater has three holes for mounting. I found that #10 machine screw was the ideal size (and my parts bin contained a number of sufficient length). It was short work to drill pilot holes (#21 bit) and tap using the 10-32 tap. Final mounting, I did resort to reaming the mounting hold slightly to allow for solid flush mounting of the primer seater on the phonolic material base.
The unit has two primer seater plugs: small and large. I did experiment with the shell holder. Other primer seater units have replaceable shell holders for each caliber. The CoAx unit holds the shells by a three-point clamp over the casing rim. As such, you have a left-to-right center/clamp and one clamp to hold the third position for accurate centering. This process does allow for proper alignment to compensate for slight deformities in primer pockets.
Depressing the handle set the post forward and into the primer pocket. From there it is a quick tightening of the Allen screws to hold the clamps in position. My first attempt was with .357 shells. Once set, I checked tolerances with ten more shells and found no binding inserting the primer post into the primer pocket.
I tried a second time using 9 mm. Unlike the .357 shells, the 9 mm were not fully prepped for primer seating and I did have a little more trouble setting the for proper centering of the shell primer pocket.
Once shells are processed through a primer pocket uniformer, proper setting of the centering of the shell should be a simple adjustment.
Loading the primer tubes appears to be a simple matter. The CoAx unit has a built-in tray where primers can be dumped and slid into the primer tube with minimal handling of the primers.