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Case head seperation vs neck split

  • Case head seperation w/partial FL size

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A poll and a request

2K views 20 replies 8 participants last post by  slayer 
#1 ·
After a great debate on another thread regarding belted magnums I decided to start a little experiment. I plan to take 2 new R-P cases in 338 win mag and load them with a max charge of either RL17 or H4831, whichever creates higher pressure. I plan to fire theses cases until I get a failure or close enough to a failure that I feel unsafe firing them again. I plan to FL size one and partial size the other and see which case fails first and where. I plan to make marks on the bottom of the cases to keep track of which one is which, as well as how many firings. I started a poll to see what everyone feels will fail first. I will also not anneal the cases. Only tumble, load and shoot.
Now the request, I would like for someone to participate in the same experiment with a cartridge of equal pressures of the 338 but with no belt or rim and also post their findings here to see exactly which design has better case life.
 
#2 ·
I think the full length sized will fail first due to the extra workin of the die everytime you load it. Curiuos to see how this works out myself.

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#4 ·
Thanks for responding guys. Due to work and coaching baseball I will be starting my testing Monday morning. After checking hodgdons data and a QuickLOAD model designed around my barrel time for Hybrid 100V I've decided to go with RL17 over H4831. QuickLOAD puts peak pressure at 57,536psi with a charge weight of 65.6gr. I will be using a 66gr charge so the peak pressure will be slightly higher than the 65.6gr model. This should also produce 2,660fps from the 24" barrel on my Ruger M77 tang safety using Hornady 250gr interlock soft point bullets.
The cases at this point have been chamfered and ran over the expander button to uniform the case mouths. I've marked the case base with my dremel. The case with the vertical line will be partial FL sized and the case with the horizontal line will be FL sized until a failure occurs.




 
#6 ·
how you FL resize will make a huge difference to the brass .. As we all know.. you can EASILLY make a case fail by bumping the shoulder excessively.

Just saying.
I absolutely agree. I will be full length sizing with the die set up as the instructions detail. The partial sizing I will stop just before the die touches the shoulder and will only bump the shoulder slightly if needed.
 
#8 ·
I finally got to shoot the 338 cases last weekend. Alliants data listed 66gr of RL17 at 2,664fps for a 250gr bullet. I was very surprised to see the chronograph read 2,850fps. If velocity is what you're after RL17 is definitely the powder for that. At any rate, I got the cases marked and loaded back up for round two.





 
#9 ·
Are you starting with a starting load or simply jumping to a max or near-max load? Are you tracking case head dimensions, case extraction, and such to be sure you are not WAY over max?
FL sizing will increase head space. Head space causes case body stretching as the shoulder is pushed forward and the head is pushed back. Doing this repeatedly will lead to case head separation, as the stretch occurs right at the web/case body interface. You should have a bent wire to feel for the beginnings of this separation during case inspection.
Most manuals show this and how to detect.
 
#12 ·
I've already done load development with the powder/bullet combination. I detected no pressure signs with the max charge of 66gr. As joe said, I started this test because of another thread about belted magnums. I picked the powder because it creates the most pressure of the two powders I wanted to use. A case failure is what I'm looking for. My testing is to see where the case fails and how many times a case can be sized(partial and full length sized) and loaded before it fails.
 
#10 ·
noylj, Did you read the his full thread? and there was another thread debating failure of cases FL sized vs. Partial length sized (among other things) and Belted vs non belted"magnums". That created this thread and his test.
 
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#11 ·
I have run the "test" over the last 25 years. Belted magnum cases when full length sized only last two to three reloads but it is gun dependent. The problem is the gun's chamber based on industry standards is longer than the FL sized case and the shoulder has to move forward during firing. That stretches the case wall and the weak point is about 1/4 inch above the rim end of the cartridge. But if your belted magnum gun happens to have a chamber with a closer fit of the case shoulder to the gun's chamber then you may not see this failure at all. If you only neck size or partially size to not move the shoulder back after the first firing then you will get longer life than if you full length size. But the first loading stretches the case to fit the long chamber and the cases start out weakened and you'll never get the same life out of them as a non-belted case in a good fitting chamber.

Non-belted cartridges loaded to energetic levels tend to burn through the throat of the case after many reloads (like more than 5 to 10). One tester using the then new RCBS X-Die got 20 reloads out of the un-belted hunting cartridge. I have lost cases due to primer pocket expansion that would no longer hold primers securely but that was after many more reloads than I have seen failures of belted magnum cases. The most common failure after many reloads of non-belted magnum cases is throat burn through. Even belted magnum case not FL sized will fail due to throat burn through but after many reloads.

The test proposed is too gun dependent and reloading process dependent to be meaningful, in my opinion. The result will be, as thousands of belted magnum owners who reload have found through the ages, that the run of the mill belted magnum gun will destroy cases with head separation in 2 to 3 reloads unless the shoulder is not moved back with a FL sizing die. The proof of that exists in spades over the last 50+ years.

LDBennett
 
#16 ·
The primer pockets still feel the same when seating a primer. I do have a couple 300 Winchester cases that aren't as tight as they once were but still not an issue at 10+ loadings. Here's a picture of the fired primers from the 338 test cases. As you can see there isn't an excessive primer flow, even at book max.

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#18 ·
Thanks.
One of these days I'm going to have to tackle the problem on my end about the loose primers. I just don't shoot my 300win mag often enough to be a pressing concern.
I have found that for my reloading needs, that the WSM cases last longer than the belted mag cases .
 
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