Cracks around flash hole.

[1951]

Cleaning some 2 time fired brass and found what appears to be cracks going out radially from the flash hole towards the edge of the pocket wall. Any one know what would cause this?

This brass had primer pockets that were too shallow so I had to deepen them with a pocket uniformer in order to seat the primers. I didn't see any sign of cracks the first time I cleaned it, will running a uniformer into the bottom of the pocket cause cracks to develop?

Thanks

 

[TAJ45]

Just a spitball answer. If the brass was under spec at the base when mfrd, already too thin and you removed more....?
If brass was not factory annealed properly before initial loading.....?
And maybe a contributing condition further down the list giving an "assist": size of your chamber.
Mix n match toward the final answer.

Like I said, brainstorming n spitballing.

 

[divingin]

Are you using a normal sizing die with an expander ball/decapper and running it in too far?

 

[358WCF]

Cleaning some 2 time fired brass and found what appears to be cracks going out radially from the flash hole towards the edge of the pocket wall. Any one know what would cause this?

Thanks

Appears?... Is it really cracking or maybe carboned up chatter marks from cutting the pockets deeper? If unsure, maybe try the uniformer by hand to see if they go away?

 

[BlueWater]

A buddy's brass is looking this way, after 5 firings.

Cracks and looking like being "eaten away" in spots around the edges of the flash holes, when viewed from the primer pocket end. I hadn't viewed it after prior firings, so I've no idea when this condition started. New StarLine brass doesn't show anything like this (of course).

StarLine brass, 6.5 Creedmoor
Not annealed
No primer pocket uniforming
CCI #450 small rifle magnum primers used, typically
No signs of over-pressure (no escaping gas, streaks, primer deformation)
No indications of wonky accuracy or velocity
Loaded with Redding full-length sizer/decapper die, Redding Competition seating die
Cleaned after each firing with rotating tumbler and stainless-pin media

 

[LHSmith]

Cracks and looking like being "eaten away" in spots around the edges of the flash holes, when viewed from the primer pocket end.


Cleaned after each firing with rotating tumbler and stainless-pin media

I checked the last batch of Lapua brass I cleaned with ss media and I notice the same thing- although it was the first time this brass was cleaned this way. I am thinking that the ss pin tumbling method creates more problems than it solves.

 

[RegionRat]

This is another good place to apply a borescope. If you wet tumble with pins, or ultrasonic clean, for the sake of a clear view, it helps get past the carbon for better visual inspection and to be able to share a few photographs.

It would also be helpful to describe the cartridge being discussed and at least a vague description of how it was loaded and used. For example a 4000 Ft*Lbs cartridge is one thing in terms of potential for damage, and a 1300 Ft*Lbs is another. Stress and strain work in different ways based on the size of the primer pocket and web thickness, so getting us into context would be helpful with respect to your past history with the chamber and the performance with other brass.

Has this rig seen lots of other loads without incident or loose primers? Does it commonly give "clickers"? Or is this also a risk due to a new chamber that might be cut too loose?

The head of the case is not annealed in order to get work hardened properties for the primer pocket and extractor groove strength, not to mention pressure containment. Soft brass would tend to flow rather than crack. A crack might form if the chamber dimensions are generous and the pressure was very high and under the right (unlucky) circumstances, but it is still a rare combination.

Did you find other signs of trouble in that brass?

 

[1shot]

How about some pics?

 

[1951]

Thank you for the replies.

I turned the uniformer across the bottom of the flash hole and most of the "cracks" cleaned up. Either it was just carbon tracks or light surface cracks that cut away. I think carbon tracks along the chatter lines left by the uniformer as suggested above. Some of the brass looks like the ones BlueWater has described, little chunks out of the corner of the flash hole where it intersects with the floor of the pocket. I kept the ones that cleaned up and tossed the others.

I don't have a camera that will take macro shots of the pocket floor.

The sizer I use is a full length one but I took the expander bulb out and use a collet sizer on the necks. I know nothing is hitting the bottom of the case.

I don't think the chamber size is excessive, the shoulder only moved two thou from what I bumped it to, and that 2 thou is right where I get bolt drag. the diameter of the neck, body at the shoulder under the head seem OK.

One thing that I'm worried about is the primers of the factory cartridges were sitting proud before they were fired, once fired they were pretty much flush with the case head. If the primers just collapsed that's fine but I wonder if the force of the primers on the bottom of the pocket when fired could have weakened the case head under the pocket?

The cartridges are S&B 6.5 creedmoor 140 grain FMJBT. Was the only ammo I could find when I bought my new rifle. Couldn't even buy any loading components then or I would have loaded my own. Have been shooting since 1955 but I am really new to this reloading stuff, just a few weeks ago I'd never reloaded anything. I don't know of anyone on the island I live on who does so I'm kinda dependent on books, videos, and hopeful some of the experience members of this forum have.

Once again thanks for the replies.
Al

 

[358WCF]

SNAFU... All of the S&B rifle brass I've seen has shallow primer pockets. 'Tis a regular problem I hear.

 

[Sandstorm]

some of the experience members of this forum

Sir this is the place to ask. You will find answers to questions you didnt know you had yet.?
among some good helpful reloading experts...i certainly have found a wealth of wisdom...as well as some crap..lol....just kiddin

 

[acloco]

Have observed cracks in the primer hole prior to stainless pin tumbling.

I DO take the sharp edge off of the flashhole, juuuuust barely though. Problem is solved.

 

[1951]

I've heard/read opinions of the S&B brass some of it not good, well most of it not good. I loaded up some used S&B brass that I had deepened the primer pocket in and some new Henderson brass, same load, bullet etc. Fired them in five shot groups and could see no difference in accuracy and the muzzle velocity was pretty much the same as well. Now if I was a more accurate shooter I may have found one better than the other but for my level I think one is as good as the other. Guess I'll keep using them, not going to fire and then go through the pain of deepening the pockets on the remaining 200 factory rounds I have left though.

 

[Oso]

S&B is some of the prettiest factory brass.... the luster is very nice. However, S&B's brass alloy (rifle and pistol) is very hard. Even with annealing it is noticeably tougher to work then cases made my other manufacturers. The common complaints are split necks and heavy spring-back when resizing cases making it hard on the reloading press and perhaps inconsistent/excessive neck tension. If it is all you have on hand then it will do, but if you have other options then maybe consider another headstamp.

 

[243winxb]

The thickness of the web can be measured & compared to other brass. After the pocket depth is uniformed, i would not remove any more brass. Use uniformer to clean the pockets only. The tool should have a fixed stop.

Very old internet photo.

 

[1951]

I don't know why I typed Henderson, it's Peterson brass I used to compare.

Thanks for the replies. The uniformer does have a stop. The S&B does look nice and I got the same result with it as I did with the Peterson, but I'm not a sub 1/2 MOA shooter.
One thing I did notice when comparing the two cases the S&B cases extracted and ejected very well but a couple-three of the Peterson extracted from the chamber but dropped onto the magazine rather than eject. But I wasn't aggressively working the bolt, just pushing it back with my thumb so I could catch the brass before it fell onto the concrete floor at the range. Most likely coincidence it was three Peterson and not S&B
Extractor groove diameter on 10 of the S&B is 0.396" and 10 Peterson is 0.402", can't see 6 thou making a big difference. Thickness and diameter of the rim is the same.

 

[ronemus]

One thing that I'm worried about is the primers of the factory cartridges were sitting proud before they were fired, once fired they were pretty much flush with the case head. If the primers just collapsed that's fine but I wonder if the force of the primers on the bottom of the pocket when fired could have weakened the case head under the pocket?

That could be the source of the tracks in the bottom of the primer pocket. It seems that the pockets were too shallow. Peak pressures of 50k psi or more drive the case head to the bolt face, which will definitely collapse the primer, and drive the anvil into the floor of the pocket; the tracks may be where the edges of anvil were pressed. Anvils are usually tripods. Were there by chance 6 tracks?

If you have a borescope you could use it to to photograph the primer pockets; the focus is usually ~1 cm and the field of view would be approximately the diameter of the case head. If it's a digital borescope (Lyman, Teslong, etc.) you get the photo directly, and if not there are many threads on digiscoping.

 

[divingin]

Thank you for the replies.

I turned the uniformer across the bottom of the flash hole and most of the "cracks" cleaned up. Either it was just carbon tracks or light surface cracks that cut away.

The primer anvil is usually a "tripod" looking thing with the peak struck by the firing pin (through the cup, of course.) The resulting flame usually leaves a hardened soot material on the base of the pocket where the anvil isn't (i.e. in either 3 or 6 points depending on priming compound, but unevenly distributed.) Could this be what you were looking at?

I don't have a camera that will take macro shots of the pocket floor.

Most late model cell phones will: Try using a brace to steady your phone/hand, stay back anywhere from 6 inches to two feet, and use the cameras zoom to enlarge the image. You may need some additional light to get a clear pic.

 

[1951]

Thanks for the replies.
All I saw on the 1 X fired brass was a pocket filled with soot, all across the floor of the pocket. After I Fired them a second time with deepened pockets I only got three patches of soot and three clean patches, like a three spoke wheel. very clean pocket compared to the first firing. Neck and interior of the case was cleaner too. Seems S&B use some rather dirty burning powder. But firing the rounds with the primers proud most likely contributed to whatever is going on with the pockets, and I don't imagine it did my bolt face any favours. I didn't notice the "cracks" until I cleaned the pockets. But most of it cleaned up after I ran the uniformer across the bottom of the pocket a couple turns. I'm convinced the so called cracks were from cutter chatter as suggested above. Don't know about the ones that seemed to have chunks broken from the corner of the flash hole and pocket floor, but I chucked those ones.

Borescope? I wish. No, I don't have one.

Not only do I not have a macro camera I also don't have a cell phone, my phone hangs on the wall with a long curly cord connecting the handset to the base.
I'm kind old fashion, and just plain old as well.

Once again, thanks.