Pressure signs - extractor shine

[Ike Arumba]

I've started reloading for my X-Bolt in .308 Winchester. I'm puzzled at seeing some shine on the case head from the extractor at charges that I had figured were comfortably below max.

I bought Prvi Partizan 168 gr "match" ammo, which I shot, neck-sized, and reloaded. The spent factory primers have by far the least appearance of pressure signs that I have ever seen. The primers on my reloads at the low end charges look much more flattened. They are Federal LR primers, which I hear are softer than others. But I don't think they look more flattened than the Winchester primers i have used for .30-30 WCF and 7.62x54R. They are not at all cratered.

One bullet I started working up a load for is the 150 gr. SPBT blem from Midway. Lee lists IMR4320 charge as 44.1 - 49.0 gr. In my previous experience with those other rifles, I had not seen any overpressure signs going up to book max from Lee or Hodgdon, so I thought I'd cut a corner and start at 46.9 gr. (Yes, I know I'll get scolded for admitting that.) No problem. The next step was 47.1 gr, and I saw a bit of shine from the extractor. Then I shot three at 47.4 gr, and saw some shine on the third but not on the first two. I stopped there. The cases just above the extractor groove measure 0.4695 except for the last 47.4 gr one, which showed 0.470. For comparison, four fired factory rounds that had not been reloaded measured 0.4695.

So now I am wondering, is the shine from the extractor a sign to back off the pressure, or is it maybe just that the X-Bolt's extractor sticks out a smidge?

 

[Kachok]

The 308 can be tricky with pressures, mine gives me major pressure signs 3.5gr below max with Varget, but with RL15 and W748 I can feed it max loads all day. None of my other cartridges do that with similar burn rate powders.

 

[243winxb]

A " shine " from the ejector hole tells me you are at or near maxinum pressures. When you can feel the edge of the shine with a finger nail, your a little to hot or brass is soft. Factory ammo has the shine sometimes. The Lee 49gr max may have been taken from old Speer loading data that is very hot & over pressure in many rifles. Hodgdon's 47.6 grs would be my maximum @ 60,100 PSI. Different Component = Different Pressure.

 

[MtnCreek]

Also consider brass being used. How does Prvi Partizan compare to Win or Rem?

 

[SlowFuse]

The PPU brass you are using may be on the thick side, causing less case capacity. I ran into this problem when using the same brand in 25-06. I had pressure signs well below max. My mistake was being too comfortable with the current load I was using and jumping .7 grains higher.

Switched the exact load to win brass and had no problems. A later volume test showed the ppu had less capacity than the win brass.

 

[Ike Arumba]

1. I don't know how soft PPU brass is compared to the others. It's conceivable that they are using soft, considering how light the recoil is for their factory load. But I haven't seen any such sign using PPU brass in the other 2 rifles with the other chamberings.
2. There is no mark from the ejector hole, just a shine from the extractor.
3. Hodgdon shows 49.0 gr max for the Nosler BT, which I figure corresponds to the jacketed lead bullet I am using. Their 47.6 gr max is for the Nosler E-tip, which is all gilding metal.

 

[Kachok]

PPU brass is thicker then other brands in my experience. So you would indeed have some loss of case capacity, on the up side it is not "soft" at all and will probably last you until the next ice age, or at leased till Obummer has to find a new job. I don't have any PPU 308 all mine are stamped 7.62x51 not sure if their 308 brass is any different.

 

[SlowFuse]

I agree with kackok. I have reloaded the same set of 20 going on 9 times with no major signs of wear.

 

[raddiver]

This is the first ive heard of this.
Can someone post a picture of what it looks like so i can get edumucated?

TIA
-RAD

 

[Ike Arumba]

photo of the extractor shines

Here is a photo of the shines.
Top left is the fired factory load, not reloaded.
Top center: 46.9 gr. IMR4320
Top right: 47.1 gr., shine on the W, extending to just short of the 8.
Bottom left: 47.4 gr., a bit of a shine on the N, and into the gap away from the I.
Bottom center: 47.4 gr.
Bottom right: 47.4 gr., shine on the gap between the P and the 3.



These shines result from the extractor ironing out the texture of the case head. A couple of the case heads look a bit out of round in the picture, but this is just due to how the chamfer catches the room light. The sharpie marks are just to tell how many times the cases have been reloaded.

 

[raddiver]

a picture is worth a thousand words.
And i see it. Thanks for the education.

-Rad.

 

[SlowFuse]

Hey Ike, I have never marked x's fired with a sharpie but I would think that will wear off when tumbled.

I do however use a spring loaded center punch on brass that I actually like to keep up with. A very slight dimple is all it takes.

 

[119er]

While not a crystal ball, a chronograph would help you to better determine where you are at. Velocity and pressure are not competely proportional but when working up from start loads it is a very good indicator as long as you are paying attention to consistent loading practices. My chrono has shown me some interesting things that did not correlate to the four reloading manuals that I use. Small things can make big changes and I think that anyone who reloads to reach the upper end of the data should be using a chronagraph.

Other than that I have wrung the poo out some PPU brass in .30-06 and it is still hanging in there. I use it in .303 British at moderate pressures and neck sizing only. I think it's great brass.

Also, check those BLEM's for diameter and see if there are any inconsistencies with roundness. If they are a little large or out of round and your brass has thick necks going into a tighter chmaber you could see high pressure signs earlier. Maybe compare the base to ogive length as well. If you are out near the rifling a slightly shorter ogive can have you in the rifling. Hope this helps and can get you on the track to finding your answer.

 

[MtnCreek]

There is no mark from the ejector hole, just a shine from the extractor.

Unless I'm missing something, I see an ejector mark, not an extractor mark.

 

[Ike Arumba]

COAL to hit the rifling = 2.860". COAL I'm using = 2.820". Would it lower pressure to shorten to 2.800"?

 

[Walkalong]

No. Reduce the powder charge.

 

[243winxb]

Overall, i see no high pressure signs that would worry me.

[/URL][/IMG] Ejector marks- Normal load right. Working up to Hot load on left, with expanded primer pocket. Primer fell out. Caused by high pressure. The primer pocket may open with 1 loading that is very hot. Or it may take several reloads at maximum to slowly expand the web area of the primer pockets. Common to Rem, Sako, Savage ejectors.

 

[USSR]

Ike Arumba,

The make of brass is critical with the .308/7.62x51 cartridge. Like Walkalong said, reduce your powder charge weight.

Don

 

[NCsmitty]

Overall, i see no high pressure signs that would worry me.

That's how I see it, as consistent light ejector extrusions indicate excess of 70,000 psi, and as 243winxb illustrates in his pics, those cases are at dangerous levels. Flat primers are often meaningless, while cratering around the FP indicates pressure, and you have none.
PPU brass has been decent stuff, and certainly the equal of other commercial brands. As mentioned, a chronograph can often sort out the mystery.
It seems that you are nearing maximum for that rifle, using the components listed.

Remember that the older powders like IMR4320 are temperature sensitive, and ammo should not be left sitting exposed to the sun on a bench as it can raise pressures.


NCsmitty

 

[Walkalong]

Overall, i see no high pressure signs that would worry me

Yep, the one bottom left barely shows something.

Did any one charge weight shoot better?

 

[119er]

COAL to hit the rifling = 2.860". COAL I'm using = 2.820". Would it lower pressure to shorten to 2.800"?

What I meant by this was higher pressure caused by a bullet inadvertently touching the rifling if you were seating the bullets to be very close to the rifling. With BLEM bullets I am always cautious in regard to variances as they were segregated from the others in a run for a reason. What those are is anyone's guess. I doubt highly that they would sell anything unsafe but its best to check anyway.

When I started I didn't have a chronograph and was paranoid about pressures. I got tired of conflicting pressure "signs". To me "pressure signs" are like symptoms that can be misleading. They can give false positives or show nothing at all when things are dangerous. A chronograph is a much better diagnosis tool. When I got one it alleviated my concerns and gave me another dimension of safety/control.

 

[Robert101]

In looking at the photo's the OP posted, I don't see alarming overpressure signs. If the cases are not difficult to extract, and it appears the primer edges are still rounded, therefore, I would not be very concerned. Your primer pockets are still tight right?

 

[Ike Arumba]

After studying the cases, I have decided that MtnCreek is right, these are ejector marks. Their appearance changes with lighting and aperture (camera > eye), and I formed my impression while at the range, seeing trapezoidal shine marks rather than circular. (The extractor is trapezoidal.) Below is a photo in which I tried to capture the trapezoidal shape. Evidently these trapezoidal shine marks come from the ejector wiping the brass as I lift the bolt handle.

The two cases shsown below were loaded with 53.0 gr. of A2520 under Sierra #2100 110 gr. RN bullets. Western Powder gave me max loads of 54.0 gr. A2520 for the 110 gr. Berger FBT, and 53.5 gr. A2520 under a 110 gr Hornady V-Max. I saw no shine on two at 47.0, two at 48.0, nor two at 49.0 gr. There was a hint of it on one of two at 50.0, and a slight bit on one of two at 51.0. I can see a faint bit of it on 1 of 2 at 52.0, although I didn't notice it at the range.


Another reason I thought these marks were from the extractor was that I expected ejector marks to protrude, since the ejector can be pushed a bit below the bolt face.

As for which loads are more accurate, it's hard to tell. Those five 150 gr. loads in my first photograph were all I shot before I decided to stop and ask for your opinions. They were not tightly grouped, though. I later realized that my scope was showing parallax, even though it was set for 100 yards on a 100 yard range. I set it for 250 yards, and then the 100 gr. loads I shot after that looked much more consistent, but I only shot two at each level. I didn't mark my targets well enough, and then I had to travel, so the targets, being over 2 weeks old, don't tell me enough to make definitive statements.

But, I will back off. I don't have a chronograph. I just wish these marks would show up consistently at a given powder level.

 

[Bruno2]

Some things that I have noticed about pressure symptoms are congruent with what others have said. Sometimes primers do strange things and it doesn't necessarily mean you have a pressure problem. The shine on the head makes me want to say you are maybe a little above max for that load. However, I always try to get a feel for how tight the bolt is when I open it. If the head of the case has some shiny spots that doesnt concern me if the bolt opens as easy as it always does. I would still back it off a couple of grains and see what it does.

 

[Ike Arumba]

Update - resolution

Hodgdon's reloading website shows the recommended load of IMR4320 as 44.1 to 49.0 grains, with Winchester brass. I brought home 9 pieces of Winchester range pickup to compare with my PPU brass, by weighing how much A2520 fine-grained ball powder would fill them to the neck.
Winchester: 57.6 +/- 0.8 (9 pieces)
Prvi: 55.1 +/- 0.4 (10 pieces)
The Prvi:Winchester volume ratio is 0.965. Multiplying this by Hodgdon's loads produces a range of 42.6 to 47.3 grains. I started picking up ejector wipe shines at 47.4 grains, which is just above the adjusted max load.