Lets talk about primer pockets

[Marine sniper]

My .300 Weatherby seems to like hot loads; running Berger 210's at over 3000 fps (80.0 grains of 7828 .005 off the lands) I primarily use Weatherby brass and after 4-5 shots the primer pockets are pretty loose. I know the conventional wisdom is the brass is dead at that point, but why? Being a little curious I got my digital calipers out and took a few measurements.

Here is what I come up with:

.2100 (diameter of unfired Fed 215 primer)
.2080-2100 (diameter of a loose primer pocket)
.2060 (diameter of a tight primer pocket)

My question is why is the brass dead, if it is, when the primer pocket is loose. As long as the primer will stay in the pocket, good enough right !! I neck turn all my brass so it is not getting worked as much as a FL sizing would do. Anybody tried to "fix" the brass so the pocket would hold the primer?

John

 

[eddybo]

Like this?

MidwayUSA - R W Hart Case Saver Swage for Large Primer Pockets

 

[Varminator 911]

???

So why is the loose as small or smaller than unfired? And how can tight be smaller than unfired? Are you telling me that the primer pocket actually gets smaller, narrower, after firing a mild load? Or am I just out of of it this morning???

And how does this punch thing work? Do you narrow the pocket by making it deeper? Is that what's happening above with a mild load?

OK, I am asleep!! 0.210 is diameter of primer, not primer pocket.

 

[Fiftydriver]

I have tested this quite a bit in my wildcats and more then anything in my 338 AM where the brass quality has declined a bit.

Its common to get spooked when you seat a primer and it seats with little pressure but I to asked is this really a problem.

My standard original load would loosen primer pockets up within 2 firings, noticably loosened. So I dropped the load back a bit for these cases, only 50 fps or so off the original velocity level.

Primer pockets would loosen up around 3-4 firings but they would still hold a primer. I continued firing the cases with this same load up to 6-7 firings and while the primer pockets were what would be considered very loose, there was still no gas leakage. I stopped at 7 firings as this is totally acceptable to me in this chambering, in fact 5 firings is what I was looking to attain.

In my opinion, if you are not seeing any gas leakage, your cases are still usable. For how long depends on the load and the brass. Many cases will expand on the first couple firings and then seem to stablize for several firings after that as far as primer pocket fit.

If your using loads that are leaving heavy ejector rings on your case heads, your pushing pressures pretty hard and your cases will not last as long so keep that in mind.

If your using a load within the specs of the cartridge your shooting, as long as the case is holding the primer with enough force that it can not move and you are not getting any gas leakage, go ahead and use them.

You can often see minute gas leakage if you take a bright light and look at the side walls of the primer pocket. If they appear matte finished at all, there is some gas getting around the primer cup lip. at times, this will only extend half way up the wall where it is then sealed off by the expanded primer cup. If the primer pocket wall is "matted" all the way up, your getting some gas leakage and generally you will see this on your bolt face.

Over time carbon will build up around your firing pin hole at best and at times you will get actual erosion in a ring around the firing pin on the bolt face. If your seeing this in any way, get new brass!!!

Kirby Allen(50)

 

[royinidaho]

--[deleted]--

Kirby was quicker on the trigger this morning,

I do what Kirby does.

 

[jwp475]

Nothing wrong with 2 answers Roy.