Case Rim Expansion - 6.5 Saum

Primer pockets both measure .209 on fired and unfired brass

I don't own any DBM's but I'm curious to know why the sheet metal body of the mag is that close to the rim diameter. .005 clearance is not what I would think is reliably functional. If it's the feed lips then that would be the problem to be solved. With the shell holder issue, there are others to try. Borrow a buddies?
Lastly, I would try sanding some of the rims to clean up any burrs from extractors etc. and retry those in the mag and shell holders.

the saum brass has a rebated rim it never comes close to the feed lips on any mag i have seen.

gut_pile said:

Recently I have began reloading with brass that has been fired one time. I am running into an issue where the rim of my brass is expanding and my brass will no longer go into my DBM and sometimes won't even go into the shell holder.

What could be causing this?

Click to expand...

High pressure- These cartridges run right on the edge of 75,000 psi. where brass will no longer spring back, after firing.

Soft brass may be another issue.

Buy new brass. Load less powder.

I can't help but think the brass is suspect.
Definitely measure a bunch of "new" cases to start with.

Especially if the pockets aren't changing diameter.?

I had to slightly open up my shell holder opening for the Sherman improved PRC brass to fit.

Case heads and case rims can expand when cases are defective or over-pressured. I've measured case head expansion multiple times in the past 15 years. But in every instance, the primer pockets have also expanded. When primer pockets expand, the case web and case head also expand.

If the primer pockets have not expanded to a larger diameter than on unfired virgin cases, then it's very unlikely excessive pressure is the primary cause of the case heads not fitting inside your shell holder. Case rims often aren't exactly 100% round. Sometimes I've rotated the case heads slightly and they will then enter into the shell holder. I've also mounted cases in my drill press and slightly reduced the diameter of the case head, with a fine toothed file and some sand paper, until they slip into the shell holder.

You can buy pin gages on FleaBay and Amazon to check your primer pocket diameter and test for loosened primer pockets (expanded primer pockets). They aren't expensive. I use them to track both small and large primer pocket diameters of my casings.

I'd try another shell holder, or two. You might find your's is simply on the tight end of manufacturer's tolerance. Also consider buying a different brand of brass. I've had some inconsistencies with Hornady brass, in years past. Especially their 375 Ruger cases.

Thanks for the help

Beluebow said:

Typically that is caused by over pressure. Or excessively unsupported chamber.

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This is the answer ^
If you are seeing pressure signs at times then you are over SAAMI max. Try backing down the load and see if problem persists

Ditch the Hornady brass.

Do you know if the brass is all from the same lot?
With the Hornady GAP 6.5 4S (RSAUM) brass, they had at least three distinct lots/runs, and none were consistent or interchangeable with another. They varied drastically in virgin dimension and brass content/weight and internal capacity. A safe load in one lot would be OK. Run the same load in another lot and it could be very overpressure.

Sorry no help here but I find this on 223/5.56 range brass. In that case, if it doesn't fit the shell holder, I pitch it. Usually assume it's 5.56 fired in a 223 AR. Over pressure.

lancetkenyon said:

Ditch the Hornady brass.

Do you know if the brass is all from the same lot?
With the Hornady GAP 6.5 4S (RSAUM) brass, they had at least three distinct lots/runs, and none were consistent or interchangeable with another. They varied drastically in virgin dimension and brass content/weight and internal capacity. A safe load in one lot would be OK. Run the same load in another lot and it could be very overpressure.

Click to expand...

It's two different generations of brass. First and third

Copied this from Olin Brass, years ago.


"modulus of elasticity- Cartridge Brass-
Material is 70 copper/30 zinc with trace amounts of lead & iron , called C26000. Material starts to yield at 15,000 PSI when soft (annealed), and 63,000 PSI when hard.
Material yields, but continues to get stronger up to 47,000 PSI when soft, and 76,000 PSI
when work hardened. Modulus of Elasticity is 16,000,000 PSI. This means to pull a 1.000 inch long strip to 1.001 inch long induces a 16,000 PSI stress.
So if you pull a 1.000 inch strip to 1.005 inch long, you get about 76,000 PSI, which is the max obtainable."

So, If brass diameter gets larger by .005" has it reached 75,000 PSI or more?
No spring back would mean over pressure.