5.7x28mm by Winchester?

At one time I had heard that Winchester had produced a 5.7x28mm load.

Can anyone confirm that this loading exists, and if so, is there any way to visually distinguish the Win. load from the other manufacturers’ loads?

Yes. Box was marked with winchester as the mfgr, E Alton IL. Never saw the cartridges, so can’t confirm/deny the headstamp.

Most of what you see now is all Fiocchi.

The label on the box in my collection reads:

on top:

5,7 x 28

on front:

Lot FNB04A970-001/16

on back:

Ammo Winchester 5.7x28 JHP 50
Brass Case Boxer Primed SS193
bar code
AMM-250 06/28/2004

The rounds are brass case, brass primer, GM HP bullet. There is a black prime annulus and three stake primer crimp. Headstamp is 5.7x28 FNB 03. They are identical in every respect and indistinguishable from the FN rounds in my collection.

If Winchester did load them they might have been for an FN contract given the FN components and lot number.

Interesting to note the headstamp date of 03 and the date on the box of 04.

Anyone else have anymore info on this? I would also like to know when firearms chambered for the 5.7 first became available for civilian sale in the US. Anyone know?