Pressure Signs On These Case Heads?

[vh20]

Hi, Everyone.
In a PM discussion with another forum member, I mentioned marks I'm getting on case heads in a new rifle that I can't explain. There are annular marks/swirls around the head where the stamp is. At first I thought they were coming from my pocket uniformer (used in a drill press), but upon further investigation they are actually coming from the rifle when fired. The rifle is a brand new Savage 110 FCP in .338 LM. It has about 50 total rounds through it to date. I can see a faint ejector stamp on almost every case unless it's from loads at the very bottom of the range. I am not seeing any ridges or deformities. But I'm also seeing these swirl marks that go a full 360 deg. around the head. They are present on every case, but more prominent as the charge increases. I am not experiencing any hard bolt lifts. I cannot see any burrs, etc. on the bolt face. Regarding headspace, fired brass from max loads tested so far measures about .003-.004" longer than factory-new brass when measured at the shoulder with a bump gauge. I can see the marks even on once-fired brass from factory-loaded ammo, but it is more prominent on the higher end of my test loads. CCI 250 primers are beginning to show some cratering around 93.5 gr, and maybe slight flattening, but not significant. Just wondering what you guys think of all this. The 93.5 gr load chrono'd extremely solid (best), and I'd like to work with it more if it isn't over-stressing the rifle. The powder is Retumbo. Hodgdon's range for the 300SMK I'm using is from 85.0 - 94.0.

OK, so on the left is once-fired brass from a Lapua factory load. In the middle is one of my loads with 87.0 gr. of Retumbo, and on the right is one of mine with 93.5 gr. of Retumbo. Ejector marks are all lined up at the 9 o'clock position in the photo. The annular swirl marks in question can be seen going through the headstamp lettering. Due to the camera/lighting angle it might not be clear, but they go all the way around the head. I'd appreciate your thoughts. Thanks!

 

[jbailey]

Re: Pressure Signs On These Case Heads?

Interesting.

Do you also have a photo of the bolt face?

 

[vh20]

Re: Pressure Signs On These Case Heads?

Ha! I was just now re-inspecting it and taking a pic of it while you posted. I haven't noticed it before, but that bright ring is brass-colored, not silver like it looks in this pic. I also went back and re-chambered fired brass from all my loads tested so far - from 85.0 gr. all the way up to 95.0 gr. (which is above Hodgdon's max of 94.0). All brass rechambers easily, BUT the marks in question become even more prominent and shiny after being re-chambered.

 

[LawnMM]

Re: Pressure Signs On These Case Heads?

I think the rings are from brass buildup on the bolt face, at the pressures involved with this caliber I'm thinking you don't need much on the bolt face for it to start marking up your headstamps.

The ejector marks aren't very bright and there isn't any wipe. I think you are on the upper limits of what the rifle can handle comfortably but I don't think its excessive. I will defer to the advice of others with more experience with this caliber but based on our prior discussion and the other thread I think you have a winning load.

Rich

 

[armorpl8chikn]

Re: Pressure Signs On These Case Heads?

There is only one ejector mark on each case. That indicates to me that only one of your loads is hot, the original factory one.
Your reloads are probably safe if I had to guess, by the evidence you have presented.
Clean your bolt face and see if the rings stop gouging deeper on the cartridge headstamp.

 

[vh20]

Re: Pressure Signs On These Case Heads?

Mr. Chikn, (cool username, by the way)
Thanks for the reply, but I don't quite follow what you are saying in the first two sentences?

Thanks

 

[armorpl8chikn]

Re: Pressure Signs On These Case Heads?

Glad you like my name.
Let me see if I can talk slower.
You have ONE elector mark on your cases. That indicates only one firing was hot enough to make brass flow into the ejector. The fact that it is on the factory fired case indicates that this is the culprit for the ejector mark. If two of your loads were causing brass to flow into the ejector you would have two ejector marks.
Why does this happen?
OK, a bit of brass flows into the ejector. The sharp face of the ejector hole shaves that little "teat" of brass. It ultimately builds up on the bolt face and the whole situation causes the galling of the headstamp. If you clean your boltface with some KG-12 until the buildup is gone it may stop galling. Whenever you shoot factory loads this will happen probably. JUst shoot them and clean your bolt face after factory rounds.
If you see new ejector marks crop up on a reload back off a bit. Ejector marks are definately indicative of running the ragged edge of pressure.

 

[vh20]

Re: Pressure Signs On These Case Heads?

Oh, I think I see now. I don't guess I fully explained the situation. The handloads shown were loaded from factory new brass, so this is from their first firing. They weren't obtained from the factory loads. I bought a box of 10 factory rounds with the rifle to test for function and obtain an initial zero, but at $5.60 a pop I won't be shooting any more of those. At the same time I bought 100 brand-new cases, and have been going through those for the handloads. The ejector stamp appears to some degree on these cases loaded down to almost the very lightest loads listed. Now, since I fired the factory loads before any reloads, it could still be that as you suggest, the brass built up from those 10 rounds could be contributing to the galling, right? But then there is still the issue of the ejector stamp appearing on almost every load I've fired.

 

[vh20]

Re: Pressure Signs On These Case Heads?

I got the bolt face clean - it only took a few swipes with a patch and some Butch's Bore Shine and it came right off. Underneath the brass smears (when viewed under magnification) are what appear to be tool marks. Possibly the culprit:

 

[jbailey]

Re: Pressure Signs On These Case Heads?

This is still interesting to me and I don't know the answer.

I will say that the 93.5gr brass is showing more primer flow than I would recommend, probably resulting in poor brass life for you. I would move down from there despite its precision potential.

As far as those swirls... I don't know.
Hope someone can educate us.

 

[armorpl8chikn]

Re: Pressure Signs On These Case Heads?

Tooling marks are probable culprit. But the brass flowing into ejector onevery load is troublesome. Ok All your loads show a ejector mark...check. New brass, factory load, doesn'tmatter...got it. Have you fired any of your brass a second time? Is there a new ejector mark? If you have a second ejector mark show up on that minimum load brass then I would think there could be a problem of some kind. Don't worry too much until a second mark shows up, specifically the ejector mark. The galling circles are simply a function of likely tooling marks and the ejector mark/brass buildup. The galling isn't going to hurt anything but the cosmetics of the headstamp.

 

[former naval person]

Re: Pressure Signs On These Case Heads?

From the way the marks are positioned, I'll bet the bolt face isn't perfectly flat all the way across. My inclination, since the procedure is relatively simple, would be to disassemble the bolt and take the bolt head to a decent machinist who can flatten the face and polish it out. Might have to re-headspace the barrel, but that is easy to do with the nut-type barrel adjustment.

 

[oneshot.onehit]

Re: Pressure Signs On These Case Heads?

Not trying to start a pissing match here but, take a sharpie marker and put a dot on the old ejector mark on your brass, then when you fire your reload I would guess that the old ejector mark will disappear do to being flattened out by the bolt face and a new mark will appear in a different location this seems to be the case most of the time otherwise we would have brass showing a ton of ejector marks in time.

Even factory loads will show marks once in a while. This is just one of the reference points watched when reloading and more so to the degree of how tall the ejector mark is. If you’re able to feel it with your thumb nail thus being a tall mark you are building some high pressure and backing off the powder some would be of high interest.

Light marks and consistent with every piece of brass would more then likely indicate being on the edge of things which can cause high pressure issues when latter exposed to shooting in high temps 90-100 degree days all day long, running your gun hard – having a hot chamber with a loaded round in it and “taking a while” to get the shot off – the saying cooking your brass. These will then cause pressure and velocity spikes, missed hits, sticky bolts when ejecting and as everyone states possible damage.

Light marks once in a while are common with some factory or reloaded ammo at times. Just keep an eye on it or back off a bit on the powder if needed.




Just my thoughts on the subject

oneshot.onehit

 

[korykhunter]

Re: Pressure Signs On These Case Heads?

Loaded for both 7mm and 338 Allen Mags never did get used to seeing those marks. Must be more common than I thought.

 

[kenmack]

Re: Pressure Signs On These Case Heads?

I see ejector marks on all three. I was wondering if the brassing was caused by machine marks imprinting on the head, but on further thought and inspection, it looks like the brass smear perfectly corresponds to the ejector position. The brass moves into the ejector hole and is sheared off and smooged onto the boltface.