Bill,

If you take a look at the Winchester Collector magazine archives, you will find the article I wrote about the Model 43 Rifles in the Spring 2016 issue.  In it I discussed what the “A” serial number suffix specifically means.  Because the “A” is not technically part of the serial number, it was not listed in the PR records.

The letter “B” on the top of the magazine follower indicates a factory item.  In regards to the ammo, the only way to determine which brand will be more accurate, is to shoot it.  Each rifle is slightly different, and will shoot more accurately with a different load.  To give you an example, I tried more than a dozen different brands and bullet types in my Model 43 22 Hornet rifle, and it always shoots most accurately with the Remington 45-gr HP factory loads.  I tried 35-gr, 40-gr, and 45-gr loads, spire-point, polymer-tip, and hollow-point bullet loads, Federal, Hornady, Remington, Sellier & Bellot, and Winchester ammo, and in the end, the Remington 45-Gr HP loads consistently shot much tighter and consistent groups.  On a good day, I can consistently put 5-shots inside a dime @ 100-yds.  Conversely, my rifle will not shoot the Winchester brand 45-Gr SP bullet loads worth a damn (nearly 3″ groups @100-yds).

Here is the link to the Collector Magazine archive – Magazines | Winchester Collector

Bert