.338 Norma Corbon cracked case necks

In the recent thread regarding the new U.S. military project towards a 6.8 rifle platform, it was mentioned that .338 Norma was in contention to become a squad machine gun of some sort to better overmatch 7.62x54R. The words “overkill” and “overpriced” come to mind, but in any case this got me wondering about the one load type of .338 Norma that I stock on the shelf.

I have had a couple boxes of .338 Norma for the past two years remain unsold (no surprise) which were originally bought from CorBon’s online store when they were in their death throws of closing up before they ran out of original stock, and before Peter Pi sold the business. I only bought them because it was an absurdly good deal - like $49 a box for 300gr HPBT loads as opposed to the usual $80 to $100 per box. In checking a box today, I saw that the one rd I pulled out had a cracked case neck, and then I checked the other 39 rds… It turns out that 32 out of 40 rds have obviously cracked case necks, some of them bad. This is Jamison Brass, and is one of only a few headstamp / brass types that I know of for .338 Norma as most of the brass is Norma brass. The cases look annealed, but something must have been wrong with the seating depth or whatever, and I can’t believe that nobody noticed this when they were hand-packing the boxes. Not that I can rectify this with Corbon now since these were apparently junk they were shoveling out the door before flipping the closed sign.

Each year I am continually surprised by the sheer volume of calibers that Jamison / Captech once handled.


Neck cracking like this is not always there at the time of packing. Sometimes it occurs in brass cases some time after the ammunition has been shipped. One case is a swelling of the lead core of the bullet, which in turn swells the bullet itself beyond the “stretch limit” of the brass case neck. I am sure that is not the only cause. You see this a lot in tracer rounds in .45, especially early Frankford Arsenal cartridges, from an expansion of the tracer compound. It also happens in the round, transparent plastic “bullet” of the .45 ACP Signal cartridges.

I wish I was more tech-minded and could give a better explanation, including the possibility of other causes.

John Moss

Sorry, John, for another different view. While the tracer compound swelling is real, I do not think it happens with ordinary lead/antimony alloys.
I think it is simply insufficient/wrong heat treatment of the brass, possibly with impurities in the brass and too small copper contents to save money.
There is a reason why brass for case making must not contain scrap copper/brass and has 72 percent copper contents. In the long run, the more expensive brass is cheaper.

I certainly see it in older tracer rds, and in plenty of different random specimens of old military ammo, but hand-loaded rifle ammo from the past 5 years? Seemed dubious to me. Maybe the issue was the brass from Jamison, and nothing that Corbon did, but they are both gone now, at least the original version of Corbon is gone.

Peelen, no need to apologize. I said that I am not technically minded, and while I have experienced this condition on ammunition, both shooting and collecting ammunition, I never cared much about what caused it. Simply not important to me. It happens - we know that - and that for me tells the whole story. There are probably other reasons for it happening as well. I was thinking that if lead cores got contaminated by moisture or contact with material that cause what we always called “frosting” of the lead, it could expand the diameter of the core (not saying that the lead itself expands, just the frosted-like contamination that can attack lead adding to the diameter of the bullet), it might split necks Easy to find out with the cartridges in question here. Pull a couple apart and cut into the core and jacket to see if anything has changed in there.

Personally, I agree totally with you that poor heat treatment (annealing) of the case necks is the likely culprit. Friction-fit bullet put some strain on the neck, but with correct annealing, this does not cause neck splits. However, it well could if the brass in the neck is to hard and cracks with the slightest expansion.

I still don’t believe this happened at the time of packing. Time causes all sorts of potential problems with ammunition components, depending on their quality, how they are stored, etc. Again, many potential forces at work there.

John Moss

I think this is quite common with Jamison brass. In my singles collection I have several bottlenecked rounds made with Jamison brass. None had neck cracks when I acquired them. Most of them now have neck cracks.

Jamison did have a lot of issues and they are now out of business.
I have never seen split necks on on new cases? But anything is possible.