Pressure signs?

[DeepMauka]

New to reloading. I originally bought some Starline brass and then some Peterson brass for my 6arc. I loaded up the Starline with midway 108 eldm 2nds .5g of book max just to get some rounds down the barrel. Gun shot like shit, but no pressure signs/issues. Loaded a bunch more same load (.5g off Hornady book max) with different bullets, now once fired brass. No issues, marks, etc. Gun shot way better.



Yesterday, with the Peterson Brass, loaded same .5g off and this is what the brass looked like on all 5 shots 3 different bullet combos:


It was virgin first firing. Average velocity was around 10fps average less than previous 1 time fired Starline. Bolt lift wasn’t noticeably bad. Definitely not as bad as the box Hornady ELD-VT I shot breaking in the barrel. Primers looked fine to me, but I don’t really know what I am looking for.





Some questions: Is this brass fine to reload? Is the Peterson just softer, or more prone to ejector marks on first firing, or am I getting close to pressure and should back off?



Will same load with now once fired be fine since case has slightly expanded/formed for my chamber? I measured a fired case and virgin case and it’s .0055” difference. I’ll bump back 2-3thousands when resizing.

 

[SDHNTR]

Starting only .5 off book max is asking for trouble. Brass has different capacities among brands. What you experienced is typical.

 

[DeepMauka]

Finally got picture to load

Starting only .5 off book max is asking for trouble. Brass has different capacities among brands. What you experienced is typical.

I guess wrongly assumed the “higher quality” Peterson would be fine with same load as the Starline.

I need to back off then if I want to continue to use the Peterson brass?

 

[EdP]

I typically start 1/2 way between published min and max using multiple sources. Not surprised you got pressure signs considering where you started.

Here is an article with lots of info on pressure signs. https://primalrights.com/information/understanding-pressure

 

[Lawnboi]

Peterson is notorious for being thick brass with less case capacity in quite a few other cartridges. Wouldn’t be surprised if this is the case.

 

[NorthIdahoDude]

Peterson is notorious for being thick brass with less case capacity in quite a few other cartridges. Wouldn’t be surprised if this is the case.

This. It actually is very high quality brass; lower capacity does not mean lower quality.

https://petersoncartridge.com/ballistician-testing-data

Basically all of those are a grain or two less than most other brass in the same cartridge.

 

[SDHNTR]

Petersen is much better brass. It’s thicker and heavier and will last longer. It will likely get you the same velocity with slightly less powder than Starline. But because of it being thicker, it will have less capacity. That will make higher pressure earlier.

I suggest you read a basic reloading manual. Every single one in existence will tell you, usually in prominent bold print, to always start at the minimum charge and work up gradually.

 

[waspocrew]

Petersen is much better brass. It’s thicker and heavier and will last longer. It will likely get you the same velocity with slightly less powder than Starline. But because of it being thicker, it will have less capacity. That will make higher pressure earlier.

I suggest you read a basic reloading manual. Every single one in existence will tell you, usually in prominent bold print, to always start at the minimum charge and work up gradually.

^^^ This 100%

Not much else that needs to be said.

 

[wind gypsy]

Agree with the others with the exception that I wouldn't expect to be able to get the same velocity based on what you shared. It's showing pressure signs at 10 FPS slower than starline which probably means you're not going to be able to push velocities with peterson quite as fast as starline.

 

[DeepMauka]

Thanks for the replies. I mistakenly thought I was well within wiggle room since the other brass was perfectly fine. Lesson learned.

Is the fired Peterson brass with the marks fine to reload again?

 

[pods8 (Rugged Stitching)]

Thanks for the replies. I mistakenly thought I was well within wiggle room since the other brass was perfectly fine. Lesson learned.

Is the fired Peterson brass with the marks fine to reload again?

Assuming the primer pockets are still tight and your resizing die sizes enough for it to chamber, yes. If the case head marks have a burr or anything you can just rub the head on some sand paper or such to flush that up again.

 

[TaperPin]

I measured a fired case and virgin case and it’s .0055” difference. I’ll bump back 2-3thousands when resizing.

Brass doesn’t fully form to the chamber until fired a few times. A lot of folks wouldn’t bump it back at all for at least one more shot, or you’re guessing at the actual amount of bump. It just has to be short enough to chamber easily so in a way it doesn’t really matter what the number is.

There’s a lot of confusion about pressure signs - it’s good to go read an article on it, but just having an ejector mark on the first firing doesn’t mean it’s too hot. It’s a sign pressures are getting up there and maybe max or over max, but it’s just one clue. Many loads that last a dozen reloads (so they aren’t over max), will show half a dozen ejector marks. If brass fails or primer pockets open up less than 5 reloads I call that over max, and shoot for 10 reloads for extra margin. If it works 10 times I’ve never had one stick in the chamber or require a hard bolt lift. If you’re uncertain then by all means shoot for no ejector marks. As always work up to maximum loads.