I think it may be a variation of a 219 Zipper but in sizing a new case down it leaves a ring around the base where it is swedging the head a little bit. Never heard of a 6x50 SAW, what is it? Not based on a 30-40 crag, head is way too big.

Tim

SAW (SQUAD AUTOMATIC WEAPON) was a U.S. Army attempt to field a light machinegun with more power than the M-16 5.56
but less powerful than the 7.62x51 NATO.

Weight of gun and ammo were both a major consideration.The first prototype was a modified M16 using a 6x47 cartridge based on the 5.56mm necked to 6mm.The 2nd try was a shortened .25 Rem. case necked to 6mm.The 3rd case was the
6mmx48mm case .410 dia on the base and the 4th case was the 6mmx50 again based on the .410 dia.case.

SAW cases are often encountered made of steel and aluminum
as a weight saving measure.

The army started the program in 1970 and ended it in 1975.
I believe it was field tested in Vietnam.

If I am wrong on any of my information ,correct me as I would like to know more about the subject myself.

WC