Flattened Primers (pics)

[WildeKurt]

I usually load 38 Special +P but since accumulating a bunch of 357 cases, I thought I'd try my hand at those. However, most of the rounds have flattened primers which I think may be a sign of high pressure. In the attached pic, the left case is a factory round and the two right ones are my reloads. I did not use a particularly hot load (6.3 grains of Bullseye under a 158 grain JSP or 7.7 grains of Bullseye under 125 grain JSP) Both loads are at or under the starting points listed in the Lee Second edition manual. Case lengths between the fired factory round and my reloads are withing .001". Any ideas what's going on?

I'm using Winchester small pistol primers, BTW.

 

[The Bushmaster]

Primers are not a way to determine chamber pressures. Flattened primers are NOT a sign of over pressure. In most cases flattened primers are caused by the primer backing out just before the case is SLAMMED back against the rear of the frame and reseated. If you see black smudges around the primer, cratering or punctured primers then you would have a high pressure indicator. The primers pictured show normal pressures. When shooting .38 Specials the pressures are not high enough to back the primers out.

 

[Walkalong]

First two seem OK, but the third is getting real hot. Primers are hard to tell pressure by, they will lie to you.

 

[The Bushmaster]

Walkalong...Even my light .357 magnum loads show flattened primers just like the last one in the photo. Unless they are cratered, punctured or show soot smudges they are just fine.

 

[WildeKurt]

None of my reloaded rounds seemed particularly hot. Somewhat tamer than most of the factory magnum loads I've fired. I kind of figured it may have something to do with the primers themselves. I've only been able to get Winchesters around here so I have nothing to compare them too, say CCI.

Bushmaster, is this backing out bad? Are factory loaded primers better seated?

 

[The Bushmaster]

No and maybe yes. I'm not sure about Factory loads. I do know that the factory usually uses a different powder then they let us use. The primers backing out and being reseated by slamming against the recoil plate of the revolver isn't a problem. This also goes for auto pistols too. It's quite normal. My .45 ACP doesn't flatten primers due to the low working pressure, but my 9mmX19 does flatten primers on a regular basis...Unless you see other signs like hard to extract from the cylinder, case head seperation, accessively ballooned case walls, punctured primers, cratered primers or soot on the edges of the primer I really wouldn't worry about flattened primers...I don't.

 

[Slamfire]

Read Tea leaves, not primers. It will be more accurate and you get a good hot cup of tea.

As stated before, unless the primer leaks or is blown, you have no idea of what is going on. Can be absolutely too high a pressure, and sometimes primers don't leak.

I like to use a chronograph. I will shoot factory ammo for a base line, then shoot my reloads. If my reloads are faster, the pressure is higher. Or failing having factory ammo, I will compare against published values. If my velocities are mid range, then I am maybe 75% safe.

 

[Walkalong]

Walkalong...Even my light .357 magnum loads show flattened primers just like the last one in the photo

I believe you too! And I have read about it. I just have never seen it from low pressure on any of my reloads. Of course, I can't remember ever starting on the bottom of data. I have always started in the middle or so. (But to all newbies - Start at the bottom!) Anything I have ever shot and looked like that was on the HIGH side of data and, so I assumed, was the start of high pressure signs.

 

[Steve C]

If my reloads are faster, the pressure is higher. Or failing having factory ammo, I will compare against published values. If my velocities are mid range, then I am maybe 75% safe.

Velocities don't tell you anything about pressure unless you are comparing loads using the same powder. You can be over pressure with fast powder and only producing modest velocities and well within safe pressure levels with a slow powder and have velocities well above factory.

The Remington case looks fine but Winchester case primer is pretty flat. Remingon cases are generally a little thinner than the Winchesters and may have a bit more case volume.

Bullseye is a fast powder and small changes in components or charge can push pressures up faster than a more forgiving slower powder. You also need to be careful that your powder measure is throwing consistent charges and hasn't stepped up the charge level as you use it.

 

[pinkymingeo]

Winchester primers flatten like squirrels on the interstate. Those don't look bad at all. At max pressures they'll be a lot flatter. The occasional leaker happens, too, often way below max loads. The best pressure indicator is extraction. The most certain indicator is KB.

 

[Doug b]

Wildekurt,my old data shows this to be a pretty good load with a powder not particularly good for a magnum case.However the new data shows you a little on the high side.
You might try a powder more suited for that case and see what happens.

 

[WildeKurt]

Doug b - I've loaded a few rounds with Unique and liked those better (actually at magnum levels they were cleaner too). Perhaps I'll go back to it. Was never fully satisfied with the 38 special loads with Unique though even the +P loads. Maybe I'll try some with Bullseye. And back off a bit on the magnum loads too.

 

[Slamfire]

Quote:
Velocities don't tell you anything about pressure unless you are comparing loads using the same powder. You can be over pressure with fast powder and only producing modest velocities and well within safe pressure levels with a slow powder and have velocities well above factory.

Bullseye is a fast powder and small changes in components or charge can push pressures up faster than a more forgiving slower powder. You also need to be careful that your powder measure is throwing consistent charges and hasn't stepped up the charge level as you use it.

Basically true. No real disagreement. However, how do you establish a baseline?

Without pressure equipment how do you determine pressure?

We do it by observing phenomena and drawing conclusions. Many of which are false. It has been shown time after time that people piece together unrelated data points, find patterns where they don’t exist, and then make predictions based off those patterns.

Primers are one of those false data points. It is generally true that flat primers mean higher pressures, and that rounded primers mean low pressures. But I have blown enough rounded primers to know that primers lie.

The way I tell if I have a fast or slow barrel is with factory components. I know those rounds have been pressure tested and are safe.

I do know that some factory rifle rounds are made from components that the public cannot buy. There are 308 rounds that perform at 30-06 velocities, and 30-06 rounds that perform at the low end of a 300 Win Mag. But if you know that, don't use those rounds as a baseline.

 

[peterotte]

WildeKurt

Have you measured case length before and after firing? I am playing around with a hornet at the moment and find that I can't read the primers too well. Vase lengthe starts to grow at some pressure level which I found to be about proportional to the load increments. I backed off a little to find the point at which no case grouth occurs but cannot 'see' any difference in the primers.

Of my first three test shots using a 58.2gr bullet seated to the same depth. My results were;

10.34gr H4227 case length growth - 0.05mm primer flattening - diam 3.4mm
10.80gr H4227 case length growth - 0.10mm primer flattening - diam 3.7mm
11.11gr H4227 case length growth - 0.15mm primer flattening - diam 4.3mm

I have no idea what all this means in terms of pressure and the hornet runs at higher pressure than a pistol so all this may be meaningless to you.

Regards
Peter