Brass discoloration after firing?

[Bigbent7]

Specs

Once fired brass
115gr projectile
4.3gr bullseye
CCi primers

I loaded up some 9mm and noticed after firing my brass there was a rainbow tint in a specific spot on each cartridge. Seating depth was matched with factory ammo and no crimp applied. No signs of over pressure as I was in the middle between the min and max charge weight. Could it be the bullseye powder I am using? I know it performs best in 45/38 but it is called for 9mm in my reloading manual. Is this nothing to worry about?




Hard to see the discoloration in the photo but it only appears when the residue marks are. It is on the same spot on every shell. I started reloading pistol ammo but have been reloading rifle for a couple years. I havent seen this with any of my rifle loads yet

[kimbershooter]

Specs

Once fired brass
115gr projectile
4.3gr bullseye
CCi primers

I loaded up some 9mm and noticed after firing my brass there was a rainbow tint in a specific spot on each cartridge. Seating depth was matched with factory ammo and no crimp applied. No signs of over pressure as I was in the middle between the min and max charge weight. Could it be the bullseye powder I am using? I know it performs best in 45/38 but it is called for 9mm in my reloading manual. Is this nothing to worry about?




Hard to see the discoloration in the photo but it only appears when the residue marks are. It is on the same spot on every shell. I started reloading pistol ammo but have been reloading rifle for a couple years. I havent seen this with any of my rifle loads yet

Bullseye is a dirty powder. What firearm are you using? Some handguns use a blow back design that will cause this type of "dirty" cartridge. H&K fluted chambers will do this with some of the dirtier powders.

[animalmother85]

...is this a problem?

Tumble it.

[DucatiRon]

No doubt that Bullseye is a dirty powder but to me it looks like a low charge was used and the brass did not expand enough to seal the chamber and some gas escaped and fouled the case. Happened to me a bit when I was experimenting with 50 Beowulf rounds.

Edit. I see that 4.3 is a mid range load. First I would double check the charge weight them bump it up to 4.4 and then 4.5 to see if goes away. 4.7 is listed max online at Alliants website and 4.6 max in Hornady 7th edition.

[cephas]

What DucatiRon said. Also would crimp to SAAMI specs. http://stevespages.com/jpg/cd9parabellum.jpg This will help increase pressure a tad. More importantly will prevent any bullet setback that can drastically increase pressures in a caliber like this.

[Bigbent7]

Bullseye is a dirty powder. What firearm are you using? Some handguns use a blow back design that will cause this type of "dirty" cartridge. H&K fluted chambers will do this with some of the dirtier powders.

beretta 92

[Bigbent7]

Thanks for the advice guys. I will try your recommendations

[Pa.Sniper]

Mine look just like that, bullseye also. I want to switch to w231 because of this, but I can't find it anywhere now.

[Mike3888]

Mine look just like that, bullseye also. I want to switch to w231 because of this, but I can't find it anywhere now.

Try searching for hp-38. Identical to 231

[Bigbent7]

Try searching for hp-38. Identical to 231

Is it damaging/weakening the brass or is it just an aesthetic thing. Also is the anyway it could damage the firearm?