300RUM case failures

[moose]

300RUM cases seem to have a short life. These are nickel FC cases showing burn thru and cracking after about the third/fourth reload and the failure rate is high enough that I usually retire brass after reload #3. It does mean I have to track every piece of brass but on the other hand, I don't shoot many rounds at a time. I've tried both nickel and brass cases and had kind of equal luck with each.

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[moose]

I track load work with Sharpie color and a notebook, it simple and doesn't need batteries.

 

[DirectDrive]

300RUM cases seem to have a short life. These are nickel FC cases showing burn thru and cracking after about the third/fourth reload and the failure rate is high enough that I usually retire brass after reload #3. It does mean I have to track every piece of brass but on the other hand, I don't shoot many rounds at a time. I've tried both nickel and brass cases and had kind of equal luck with each.

View attachment 437067

If you have not tried annealing, you might try it with that one.
Plated cases....not a fan.

 

[DizzyJ]

How far are you bumping the shoulder back?

And yes, I agree, anneal after every firing.

 

[moose]

If you have not tried annealing, you might try it with that one.
Plated cases....not a fan.

How far are you bumping the shoulder back?

And yes, I agree, anneal after every firing.

I have tried annealing and I'm getting about the same results with any combination of plated/not plated/annealed/not annealed. The nickel plate is definitely more brittle but the failures seem to more related to it being a big case, a small hole, a steep shoulder and a lot of powder.

I know they made a 7mmRUM. I wonder if its problems are worse.

 

[Certaindeaf]

Might just be the nature of the beast but I'd be tempted to do a chamber cast of that rig and or try different brass.

 

[moose]

I think the choices for brass are Federal, Remington or Norma with the Norma to be considerable more expensive than RP or FC. Lapua is rumored to considering making it.

I've been working thru a variety of powders too but that hasn't affected case loss much. One thing I learned is always use a mag primer. Click....wait for it....boom!

 

[Greenbug]

Have you tried just neck sizing? How far are you bumping the shoulder back? Are you at the top end of the load range, running hot? What do the other end of the cases look like, flattened primers?

Sounds like you know what you are doing, just some random thoughts here....

Best of luck!

 

[moose]

I do a full resize mainly because they tend to grow. Case length has to be checked every reload. It's a finicky caliber to reload, there is even a very fine line between too little and too much case lube.

I'm not particularly running hot loads, my objective is accuracy and energy on target, not the fastest time to target. I'd much rather lob a 200 - 220 gr on a rainbow trajectory than let rip a 150gr flat sizzler.

 

[DizzyJ]

I do a full resize mainly because they tend to grow. Case length has to be checked every reload. It's a finicky caliber to reload, there is even a very fine line between too little and too much case lube.

I'm not particularly running hot loads, my objective is accuracy and energy on target, not the fastest time to target. I'd much rather lob a 200 - 220 gr on a rainbow trajectory than let rip a 150gr flat sizzler.

But how far are you bumping the shoulders back?

Do you have the tools to measure this?

 

[moose]

Oh I see what you are saying. I don't usually do a full smash with the FL die, I usually work with the rifle bringing the case back about a thousandth at a time get it to chamber. I'll do the same with OAL, looking for the start of the lands, bullet seating can be weird too as some of the big/extruded powder loads have to be compressed. I have a set of micrometers and calipers so I do measure most things.

 

[DizzyJ]

Oh I see what you are saying. I don't usually do a full smash with the FL die, I usually work with the rifle bringing the case back about a thousandth at a time get it to chamber. I'll do the same with OAL, looking for the start of the lands, bullet seating can be weird too as some of the big/extruded powder loads have to be compressed. I have a set of micrometers and calipers so I do measure most things.

Ok. Cool.

 

[moose]

Ok. Cool.

It doesn't mean I'm doing it right and not causing my own problems . Like I usually do.

 

[jordanka16]

You would probably get more life out of them by using non nickel cases, and turning necks and using a bushing sizing die, but I don't know it would be worth it. A chamber cast might not be a bad idea, the neck area might me excessively large, have you measured the neck diameter of fired cases?

 

[DizzyJ]

You would probably get more life out of them by using non nickel cases, and turning necks and using a bushing sizing die, but I don't know it would be worth it. A chamber cast might not be a bad idea, the neck area might me excessively large, have you measured the neck diameter of fired cases?

This would be quite telling.

 

[moose]

I'm about done with the FC nickel plated cases and the next batch is RP brass. I may engrave a ID on the headstamp before they get ugly and I can track case growth, trimming vs powder, charge, failure rate, etc. Hey, its a hobby It should take me while to use these up.




Here's a line up of some stages of brass. Left to right: failed, fired reload, new un-primed, my reload, factory.



Measurements for all of the above. (outside neck, length)
burnt: .334 - .336, 2.840
fired: .344, 2.843
new: .334, 2.844
reload: .338, 2.841
factory: .339, 2.840

Max case length is 2.850 and trim-to is 2.840

 

[P7M13]

That's surprising.
+1 to the chamber cast.
Find the setting on your dies where you just bump the shoulder.
My method of determining "shoulder bump" is crude, perhaps others can weigh in.
Here's how I do it:

1. Deprime, clean
2. Insert die as normal (run ram up with shell holder, screw die into place until it touches shell holder, tighten 1/4 turn).
3. Back die off 2 turns.
4. Measure case neck OD.
   
5. Lube up case body, neck and shoulder nicely so the resistance you feel is the resizing of the neck and case, not friction.
   I also lube the expander ball.
   
6. Run case up.
7. Measure neck all way to base of shoulder. Should be same.
8. Keep incrementing by 1/8 - 1/4 turn until neck is uniform.
   
9. At this point, you can do a "plunk" test to see how well the case fits with zero resistance to closing the bolt.
   
10. Once it's uniform, a 1/2 turn give you a bump of ~.0035". I've read some bump only by 0.002". I'm not a good enough marksman to note the difference.

Not sure, but if you dip the neck of the nickel cases in Birchwood Casey super blue, would it help identify any developing cracks? If it does, that would be a good test to see what cases have already failed.

FWIW, I'm getting great life out of my nickel cases, 338-300 RUM (also known as 338 Edge). Some are already on load #5.
I anneal after every 2 shootings. I anneal 338 Lapua every 2-3. I'd swear I can feel the difference in the resizing process, but I may just be deluding myself.

 

[moose]

All excellent ideas. Thanks and I'll be applying them next go-round. Repeated annealing is an interesting idea.

Most of the failures are simple neck cracks or splits (anecdotally, burn thru seems more common in nickel and cracks seem more common in brass) and they are easily detected as there is no tension to hold the bullet. And that's if it gets that far, I find most when either ejecting or after cleaning.

 

[jordanka16]

I don't know if you have a comparator, but without one it is difficult at best to measure how far back the shoulders are being set, they're also very useful for measuring OAL from base to give, which gives more consistent results.

Hornady Lock-N-Load Headspace Ga 5 Bushing Set Comparator - MPN: HK66

 

[moose]

Since I'm using the rifle as spec and not a stated norm as I'm only loading for this rifle, I think its just working the brass harder to get to spec. From what has been said, casting the chamber would quantitatively be the spec, and again, for this rifle.