Pressure signs?

[Woobie]

I can buy into around .001" on that setup but I don't believe you could accurately claim less than .0005" runout with that rig even if you had a .0001" indicator. I seriously doubt the brass itself runs that perfect.

Matt

I would say you're right. I use Wilson neck sizing and seating dies, and have gotten down around .0010 to .0015 on a few, with most being closer to .0025-.0030. If you sorted out a few pieces and worked from there you could do better, I suppose. I actually think neck concentricity is way more important than cartridge concentricity (within reason). I turned the necks on my Winchester brass. But with the primer pocket issues I was having, I abandoned ship on that and went with the Hornady. Accuracy is just as good, if not better, and I didn't bother turning necks on it. If I were to rebarrel I would probably turn necks again. But that doesn't necessarily mean you will have better overall concentricity.

Oh, and, I'd say you're right about your .0004 expert. The Internet can not be bothered with substantiating claims. But I like it when people say stuff like that. It clues me into who is spewing BS so I know not to listen to them.

 

[Broom_jm]

Here is a very interesting video showing two things: Neck sizing helps with runout and some Lee products are not just good values, they're damn good products.

https://www.youtube.com/watch?v=RZEas38vkKg

 

[AmmoManAaron]

My Ruger P95 pistol does the same thing with factory ammo. Some brands worse that others, but always the same bulge at the perimeter of the primer strike.

Oversized firing pin hole in the breech face or a weak firing pin spring or striker spring can cause cratered primers with factory standard pressure ammo. Absent any other pressure signs with factory ammo, I would check those two areas. Not a huge deal, but not ideal either since a bit of that brass can get sheared off and stuck in the firing pin hole causing problems.

 

[Broom_jm]

The interesting thing about measuring for excessive pressure is that most reloaders don't know where to start, have the proper tools, or know how to read it, if they do.

Presuming you don't have a too-generous chamber in your rifle, measuring case head expansion of brass that was already fire-formed to your chamber, is the most meaningful way to measure your brass for signs of excessive pressure. The problem is, almost nobody fire-forms their cases on purpose, while even fewer have a micrometer to check case head expansion, which is measured in ten-thousandths. Almost no one knows how big the case head of a fired case should be when it comes out of their rifle; they don't check brass before and after, because they don't own a micrometer and couldn't read it, if they did.

If the OP really wants to KNOW if those loads were unsafe, there are better ways to tell (including the use of a piezoelectric transducer and strain gauge) than JUST looking at primers or detecting premature incipient case head separations. All we really know for sure is the primers from these loads were dimpled while others fired from the same gun were not. What the chamber pressure was, or what damage was done to brass or rifle, would be purely speculative.

Now, if the OP has a micrometer (not dial calipers) he could measure the case head dimensions (just forward of the web) of a few factory rounds and compare those numbers to the cases he suspects were over pressure...but that would have to be done before they are resized. The fact that the cases were a lot harder to size tells you that the case heads probably DID expand too much, but exactly how much is very good information to have. You'd be amazed how little CHE (case head expansion) it takes for sizing to become very difficult. Just .0003" will get your attention, if your dies are on the tight side.

 

[Notalentbum]

I still have several unsized that I can measure. I do have a set of tenth mics at home so that's not an issue. The problem comes trying to figure out which cases were fired in the AR and which from the Savage. There were a few I tried to resize where the die was shaving brass in this head area. Those were going in the trash because I think they are too far gone to reuse.

Matt

 

[Notalentbum]

I finally mic'd a handful of my fired rounds. SAAMI specs the large OD just in front of the rim as max .4708. I mic'd a handful that were still unfired and they checked a pretty consistent .4685". Checking a handful of the fired rounds showed they were pretty blown out. .475-.476 was pretty common but I also had a few that only checked about .471.
I have to guess the ones that were really blown out were fired from my AR-10 where a much larger area of the case is unsupported by the chamber compared to the bolt gun.
I think the blown out cases are headed for the trash can rather than risk having one fail. The others should be okay, I hope.

Matt

 

[Woobie]

Oversized firing pin hole in the breech face or a weak firing pin spring or striker spring can cause cratered primers with factory standard pressure ammo. Absent any other pressure signs with factory ammo, I would check those two areas. Not a huge deal, but not ideal either since a bit of that brass can get sheared off and stuck in the firing pin hole causing problems.

Yeah, pressure signs are definitely not always pressure signs. I noticed when I was priming the aforementioned crummy Winchester brass that some of the primers seated very easily, while others were normal or even tight. Lo and behold, when I start checking the fired cases, I had some primers backing out. So you do have to look at the totality of what is going on.

 

[2in1evtime]

I would use a 2nd set of scales and be sure you are really loading what you think your loading!!

 

[Broom_jm]

Yeah, pressure signs are definitely not always pressure signs. I noticed when I was priming the aforementioned crummy Winchester brass that some of the primers seated very easily, while others were normal or even tight. Lo and behold, when I start checking the fired cases, I had some primers backing out. So you do have to look at the totality of what is going on.

Interesting...I've had that exact same problem with Federal 308 brass. I can't ever remember a loose primer pocket with Winchester brass, but I'm sure it happens.

 

[Notalentbum]

I'm a bit embarrassed and now ever more curious.
After all this brass showing pressure signs while some only showing very minimal or none, I decided to redo ladder tests on both IMR4064 and Benchmark. I figured while I was at it, I'd do one for Tac and one for CFE223 just to have known alternatives. Once I got the 4064 and the Benchmark rounds loaded I got in my ammo cabinet for some boxes. I pulled out the boxes and was surprised to see they were full of spent rounds and labeled as the 4064 and Benchmark I had been testing last time out. From this, I figured out that all the rounds that had the pressure signs I had been looking at all had been shot out of my AR-10 and the empties in these boxes were what I had shot from my Savage bolt gun. Surprisingly there are no pressure signs on any of these rounds. They were all Winchester brass and Winchester primers so I had sorted by headstamps when I loaded these.
So now I have a couple questions.
Could a load be perfectly suitable in my Savage bolt gun but be way too much for my AR-10?
If that's the case do I need to do a ladder process for the AR or do I just pick a charge weight that doesn't show over pressure and load away? The complete lack of pressure signs on these Winchester cases really confuses me now.
I guess I'll continue my plan and load ladder trays for Tac and CFE223 today if I have enough brass with same headstamps.


Matt

 

[Dentoro]

I know a 9mm is far different than a.308 but I have two that leave that exact same pucker mark on primers, reload or factory. That being said, safety, safety shoot. Back off the powder a bit if you feel uncomfortable, better for you and the gun.