Home Forums Hunting & Shooting Ask The Gunwriters Brass color/age question

Patina.

I am using Frankford and Denver arsenal brass, dated from the early forties, cleaned and annealed, in an 8mm-06. The color on it tends toward a very faint reddish copper hue compared to current production commercial. No signs of failure yet, 3rd or 4th firing.

It isn't patina. That is removed by your tumbling process.

Brass used to make cartridge cases can vary a bit in composition. Nominally the alloy known as "cartridge brass" is 70% copper/30% Zinc, but in practice the alloy may have rather less Zn, down to about 20%, and perhaps even a little less. The less Zn, and therefore the more Cu, the redder the material is going to be.

Another thing that can make the cases appear redder is dezincification, which is the selective removal of Zn by leaching/corrosion. When this occurs it seriously weakens the brass. You'd typically see white powdery corrosion product on the (unpolished) cases, and a degree of roughening of the surface if this was the case. You'd probably also notice signs of breakdown of teh boxes, and dezincification is typically associated with storage in damp conditions.

If dezincification isn't evident I wouldn't worry about the minor difference in colour. I'd be more concerned that the brass is sound. I'd check inside each case for signs of necking (incipient separation), and check the neck and shoulder for signs of cracking. If all's good I'd sort it according to weight, anneal the necks and put it into service.

It isn't patina. That is removed by your tumbling process.

Brass used to make cartridge cases can vary a bit in composition. Nominally the alloy known as "cartridge brass" is 70% copper/30% Zinc, but in practice the alloy may have rather less Zn, down to about 20%, and perhaps even a little less. The less Zn, and therefore the more Cu, the redder the material is going to be.

Another thing that can make the cases appear redder is dezincification, which is the selective removal of Zn by leaching/corrosion. When this occurs it seriously weakens the brass. You'd typically see white powdery corrosion product on the (unpolished) cases, and a degree of roughening of the surface if this was the case. You'd probably also notice signs of breakdown of teh boxes, and dezincification is typically associated with storage in damp conditions.

If dezincification isn't evident I wouldn't worry about the minor difference in colour. I'd be more concerned that the brass is sound. I'd check inside each case for signs of necking (incipient separation), and check the neck and shoulder for signs of cracking. If all's good I'd sort it according to weight, anneal the necks and put it into service.