Dave & Zac
Thanks for the input.
It appears that the Lab may have a HPT cartridge on the '49 FAT1E1 case. If so, it would lend some weight to mine being authentic, although it would still be one that is not documented.
The E1 case HPT makes sense. The first really comprehensive tests of the prototype rifle (T25) paired with the prototype cartridge (1.95" case) began in 1948/49, and continued through 1950. That’s why you will find such a large variety of FAT1E1 cartridges (Ball, API, AP, Tracer) headstamped FA 49. But, you’ll also find many of those same cartridges with an FA 48 headstamp. So, why are there no documented HPT cartridges with a FA48 or FA49 headstamp? It would seem to me that the very first thing that FA would have done when making a change in case design (T65 to FAT1) would be a HPT cartridge.
But, that’s not the only uanswered question. All we can do is keep looking.