Yet another brass question.


Ruger GP100 fan
November 25, 2010, 02:45 PM
On another thread the problem of primer pockets loosening before any other damage causes the need to throw out a case was discussed. I had asked (I think on that thread) about whether or not most re-loaders clean out the pocket before reloading and a number of members wrote that they never touch the primer pockets. So now my question is: could pocket loosening be hastened by not reaming the flash hole at least every couple or three re-uses of a case? I recently bought a hand tool to face the bottom of the pockets so every piece is the same and a flash hole reamer that also champhors the inside of the hole. As I understand from reading the reason the pockets loosen is because of the enormous spike in pressure that occurs in the pocket when the primer detonates. Could it be that tight flash holes do not allow the pressures to drop fast enough as well as causing an even higher pressure spike simply by restricting the movement of the pressure out of the pocket? So far my brass has held up well after 6 reloads,but curious as to whether reaming the flash holes will prevent failure before the (not annealed) necks do. I'm going to try my hand at annealing next.

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November 25, 2010, 02:52 PM
What caliber are we talking about? As long as you aren't using full power loads, brass usually holds up for many many loadings.

November 25, 2010, 03:33 PM
It has very little if anything to do with flash holes, or primer pocket pressure.

The only two ways a primer pocket can become loose is either:
From wear after seating primers in it over & over again.

Or, dangerously excess chamber pressure swells the whole cartridge case web, causing it to get bigger around, and the primer pocket wall to go along for the ride.

Trimming & deburring flash holes only needs to be done once in the life of the case.


November 25, 2010, 05:35 PM
Some brass, specifically Federal, is said to be softer than other brass and the primer pockets loosen faster than in other brands even with OK pressures. From my experience with Federal 308 Winchester brass, I believe this to be true.

November 26, 2010, 01:46 PM
I choose to believe that cleaning primer pockets makes them looser. That way I can skip that step. ;)

November 26, 2010, 07:40 PM
Pressure is the prime culprit. Loads that trash brass are a sure sign of stupid. 99% of firearms stopped grouping long before you impact the primer...let alone primer pocket. I won't tell you how or how long it took for me to learn that lesson.

Load well and live long!


November 26, 2010, 08:12 PM
federal brass by any chance?

Ruger GP100 fan
November 26, 2010, 11:23 PM

November 27, 2010, 09:59 AM
As RC said, it's not pressure in the primer pocket that does it. Remember the case head is NOT supported in most firearm chambers. That's why the case head is thicker there. Excess chamber pressures cause the brass to flow making the primer pockets bigger, hence looser for primer fit.

You just have to get past the myth that primers are so darn explosive. They're just a spark plug to ignite the powder. While I suspect there's pressure developed in the pocket when the primer fires, it certainly isn't enough to swell the pocket. Not saying they shouldn't be respected for their power, or danger.

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