Vertical Split case (body) fireforming

[Phys86]

I fireformed 14 cases today, and had two of them split vertically in the body. I've never had this happen.

Lapua 284win virgin necked up to 30 cal, fireformed to Ackley improved. They chamber with a slight resistance.
55.0gr imr 4451
175 smk 0.020 off lands
Cci200

FF velocity average 2690 from 24" bbl. Velocity of the two that split was in line with the others.

This load is well within Max in Sierra's load manual for 30-06. My FF brass as a water capacity of about 70 grains.

Could this be caused by a defect in the brass? This load is definitely not high pressure

 

[fkimble@charter.net]

Yep, defective brass.

Frank

 

[Bill Norris]

Primer and brass head stamp looks like it was a safe load. I'd go with defective brass on that.

 

[searcher]

Curious. Did the bases of the brass expand? Have your fired that same powder charge in that rifle before? I ask, as I found a few of their loads way too hot for my rifles. Offhand, I recall one being their 69 SMK load with Varget in a particular .223. I also have a .22 Nosler that pretty much won't shoot anybody's mid-range load without having pressure issues. It shoots "max" velocities using just over starting loads.

 

[Phys86]

Curious. Did the bases of the brass expand? Have your fired that same powder charge in that rifle before? I ask, as I found a few of their loads way too hot for my rifles. Offhand, I recall one being their 69 SMK load with Varget in a particular .223. I also have a .22 Nosler that pretty much won't shoot anybody's mid-range load without having pressure issues. It shoots "max" velocities using just over starting loads.

Which part of the base exactly? Rim? Extractor groove? Just above extractor groove on edge of head/groove?

Yes I've fireformed with this load in Lapua and Peterson before and it's always seemed like a middle of the road (pressure wise) load. I've shot nearly 400 rounds of 185 juggernauts through the barrel at 2825fps with Peterson brass which seems to be a very warm load compared to this FF load based on the measurements I've taken and I've never had an issue.

I would think if this were a pressure issue, there would be obvious pressure signs on the base, like ejector hole marks, primer flattening, etc. I definitely started seeing that in this Lapua brass when pressure testing with 58gr of h4350 and 185jugg in an fireformed case. So, I do not think this load is at high pressure.

 

[Phys86]

I would agree that with all the evidence and previous experience with this chamber, it is likely bad brass. If that is the case, I'm just really surprised that there's 2 of these in the first 50 cases in a box of 100 Lapua!

I will cut them in half to examine at some point in the near future, and I'll also contact Lapua support, just to inform them and see if they would be willing to inspect them if I sent them in. I wouldn't expect them to do anything for me since this is a wildcat, but they should be able to make their own assessment and determine if they have/had a problem that should be addressed.

 

[46and2]

I would agree that with all the evidence and previous experience with this chamber, it is likely bad brass. If that is the case, I'm just really surprised that there's 2 of these in the first 50 cases in a box of 100 Lapua!

I will cut them in half to examine at some point in the near future, and I'll also contact Lapua support, just to inform them and see if they would be willing to inspect them if I sent them in. I wouldn't expect them to do anything for me since this is a wildcat, but they should be able to make their own assessment and determine if they have/had a problem that should be addressed.

If you have a ball and anvil micrometer you can see if the case neck is thinner on the side that split. This would indicate the thinner side throughout the body.

Though I've never seen Lapua neck thickness concentricity vary by more than a thousandth.

 

[nmkid]

Would it make any difference that you are fireforming and your bullet isn't into the lands?

 

[Zero333]

What @nmkid said..

Either Jam the bullet hard into the lands and use a mid range load,....

or Make a false shoulder on the neck before reloading the brass. It will act as way to trick it into having the proper headspace.

Otherwise a true improved should close the bolt with the standard original round very tightly. Thus having a very tight headspace.

 

[Murray Brook]

I would think that bad brass is the culprit here. Headspace will cause a horizontal separation/crack . This is a vertical separation/crack . Never really seen this before, or at least as bad as this. JMO

 

[piie]

It almost looks like the crack is bending inwards? If that is the case - were these the first two rounds you fired? If so, was it raining/moist/humid - thinking you might have had water/oil on those two cartridges...

 

[doctorh]

Like zero 333 said,put the bullet in the lands ..015 or better and reduce power charge by 1 or 1.5 gr.looks like pressure is okay base on primer but there is a lot of stretching going on when fire forming to ack.improve.

 

[Phys86]

Would it make any difference that you are fireforming and your bullet isn't into the lands?

What @nmkid said..

Either Jam the bullet hard into the lands and use a mid range load,....

or Make a false shoulder on the neck before reloading the brass. It will act as way to trick it into having the proper headspace.

Otherwise a true improved should close the bolt with the standard original round very tightly. Thus having a very tight headspace.

It almost looks like the crack is bending inwards? If that is the case - were these the first two rounds you fired? If so, was it raining/moist/humid - thinking you might have had water/oil on those two cartridges...

Like zero 333 said,put the bullet in the lands ..015 or better and reduce power charge by 1 or 1.5 gr.looks like pressure is okay base on primer but there is a lot of stretching going on when fire forming to ack.improve.

It's headspaced correctly per Ackley and I get resistance in loading a round from the shoulder neck junction interference fit. There's incredibly minimal brass movement here compared to most Ackley's. A lot would having a 30-284 AI is a waste of time compared to a standard 30-284! Haha

The weather was dry. No moisture in the chamber. Of the 14, the first one happened midway through and the 2nd one was the very last shot. The brass definitely doesn't curve inward towards the split. I think it's just the photo. There's no rough spots or anything in the chamber than would cause it. Definitely an internal case issue.

 

[Coyotefurharvester]

Did the shoulder get formed like "normal", the rest of the brass? If they aren't formed, than the brass ruptured before pressure maxed out? I have seen cases like that before, not my brass, maybe funeral brass?

 

[J_idaho]

Sorry if already asked. Curious if it’s on thin side of the brass.

 

[Webster]

I would agree that with all the evidence and previous experience with this chamber, it is likely bad brass. If that is the case, I'm just really surprised that there's 2 of these in the first 50 cases in a box of 100 Lapua!

I will cut them in half to examine at some point in the near future, and I'll also contact Lapua support, just to inform them and see if they would be willing to inspect them if I sent them in. I wouldn't expect them to do anything for me since this is a wildcat, but they should be able to make their own assessment and determine if they have/had a problem that should be addressed.

Don't cut them all in half. Lapua may want to see a few as is. Structure wise cartridge brass should be very uniform in mechanical properties. The only thing that I would first suspect is a case extrusion forming defect. The cases are extruded to the extreme going from a flat disk to a long cartridge case. Look for an area with a very thin wall. About the only thing you can do is cut one case and measure wall thinkness variation mid length of the body and neck with a ball mike. I would weigh some good and bad cases to see if the bad ones don't weigh as much. Anything else would require a metallurgy lab. It would be interesting if a case a manufacturer would be forthright enough to tell use what defects they find during case inspection.

 

[K22]

This may not be helpful, but I have seen this before. The appearance of cases in your post was exactly the same as what I saw.

However, I've seen this only once before in bottle neck rifle cartridges but quite a few times in straight wall cases. The bottle neck rifle cases of a friend were 270 Win loaded over 15 times with max charges of IMR 4831.

In heavy 357 magnum charges, I started getting this type of failure in some cases after only about 15 reloads while other cases in the same lot, sized and shot the same number times with the same load lasted over 20 reloads. Thus, even cases in the same lot failed at different rates.

However, there is another situation I encountered with mild target loaded 38 special cases with the exact failures after loaded over 30 times.

The common element is these situations was that some cases just thinned to the point of failure due to too many cycles whereas others, being more robust lasted longer.

While this may not be the exact cause with your situation, it does seem to indicate that those specific cases in your post are just not as robust as the others in the same batch.

 

[Phys86]

Did the shoulder get formed like "normal", the rest of the brass? If they aren't formed, than the brass ruptured before pressure maxed out? I have seen cases like that before, not my brass, maybe funeral brass?

Sorry if already asked. Curious if it’s on thin side of the brass.

Yes, the cases seemed to form normally and all measurements on those matched the rest. I think it must have happened near the end of the bullet travel. If it happened at peak pressure, I would think I'd see some gas cutting in the chamber. There's only heavy carbon in the spot the case ruptured.

I forgot to measure the neck thickness of these two. I'll do that tonight.

 

[Phys86]

Should I completely discontinue use of the rest these cases? It seems there's no telling if there's others that are bad. I guess I could weigh them all and cull any that are abnormally light.

I don't think Lapua would give me a firm answer on that.

 

[Evlshnngns]

Good idea on checking weight. What is the variance in the 14 already fired?