Too much pressure or bad primers

[Derf00]

I recently loaded up some .357 rounds as follows:

Remington Brass, MagTech 158 JFP, Winchester SPMP, and 16.2g H110. They shot great and were quite accurate and I saw no signs of excessive pressure on the cases, and the firing pin indent looked ok, but the primers appeared to have filled the primer pocket.

The following was posted by swmike:

When using primers to evaluate pressures, some consideration should be given to the type of primer used as well.

I recently loaded a large quantity of 9mm using CCI primers. In the batch 100 cases were primed with Winchester primers.

Shooting the same bullet, the same powder load, and comparing cases of the same manufacturer, the Winchester primers had expanded to fill the entire primer pocket, including the chamfer. When the primers were removed, the winchester primers were "mushroomed" while the CCI primers were not. None of the cases showed signs of overpressure, just the mushroomed winchester primers.

Could this be my problem? I don't think the load is excessive. The mushroming did not become apparent until I started to reload the cases.

[Clark]

I find that H110 is hard on the primer and Bullseye makes sticky cases.

I think this is becuase the flash hole acts as a delay line, and the slower burning H110 has time to get the pressure through. The Bullseye has a higer peak pressure, but for such a short time it can only stretch the case radially in the combustion area.

What does it all mean?
H110 can make flat primers and not have peak pressure too high.

Hodgdon posts 16.7 gr on their website, and they have been known to use the wimpy finegal factor.

[mjrodney]

Grant Cunningham, a revolver smith of some reknown out of Oregon, rated the relative "hardness" of primers to me, during discussions on reducing a revolver's hammer spring weight.

Federals are the easiest to set off, having either thinner or softer metal caps.

Winchesters are close second.

CCI primers are the stiffest, however, and a lighter hammer spring may not be able to light them up consistantly.

It may just be the difference in primer cap strength.

[swmike]

Your load is less than the "do not exceed" of 16.7 gr. as shown in Lee's "2nd Edition". I found that my 357, if the cases and primer indents looked ok, I didn't worry too much about the primer flattening. I have just resolved to use only CCI primers as they don't flatten like the Winchester SPMP's I have used (also the WSP's). Pay close attention to the case, looking for the beginnings of "head separation" and "case mouth splitting".

[Ben Shepherd]

Primers look like a stovepipe hat when you pop them out?

Not really a problem if there are no other pressure signs....
Remington brass has a very generous curve radius going from case head to primer pocket vs most other brass in this particular caliber. More of a gentle curve than a sharp shoulder.

You are under current posted maximums and should be OK. But I would check 3 things:

1. Sticky extraction?
2. Measure the case down in the case head area before and after firing. If you're getting expansion there, I'd back it down a bit.
3. The primer pockets aren't expanding are they? A fired case will still hold a new primer correctly? The old primers aren't almost falling out?

[Derf00]

Thanks for the info. I knew the load was not excessive and within Hodgon's 3% range. All brass is either new or once fired and the primers seat firmly. Extraction is smooth from my 4" 686 and 6" GP 100. The only thing I haven't done is measure the case in the head area, which I will.

[mrawesome22]

I'm a firm believer that flat primers have nothing to do with too much pressure. Factory rounds flatten primers. And I guarantee that ammo makers aren't going to make ammo that would blow a gun up do to the fear of law suits. And if a powder company is confident enough to post a load on a wed site for all the world to see, I'm sure it is totally safe.

[Buckythebrewer]

JMO,But I think primer signs are very real but hard to tell sometimes.One thing for sure,,If primers fall out of the primer pockets or there are Blown holes through them then things are way too hot..Sometimes the bolt face can have a chamfer or loose firing pin that can make things look over pressure(My bolt Was like this from the factory).I have seen the differance between maybe Hot and definatly HOT as far as the primer flowing to the out edges of the pocket.There is also the differant primer hardness that throws you off easily..Keep it safe and follow load data from manufacturers or books like LEE
I will add ,shooting 223 rem ammo has always been fine with the flatteneing like Mrawesome 22 mentioned,Then I have also used mylasian 5.56 in my chamber(NOT so smart)and functioned fine yes,but I came close to having a head case seperation with one of the rounds and the primer pocket was so enlarged that a used primer would rattle around inside it.All the primers(and they were much harder than my winchester primers I load with)were flat and to the edges with the firing pin part of the primers almost blown out...Now if I was shooting On a HOT day I might have blown my rifle to pieces I don't know...Lesson learnedWith 223 remington chamber USE only 223 remington ammo,and if I have a 5.56 NATO chamber than I will be fine with both..

Warnings are for safety.And my slightly tight chamber proved it to me..Lucky I have Nine lives
I just wanted to mention what was already said as well.I use winchester primers more than any other primer and find they are very soft in comparison to others.I use them as an early warning sign.They do mushroom to the outside edges when other don't.Its not a big deaL it just scares you at 1st.But I have learned to read them for the most part..

I have to disagree on the split necks.I can make my necks split just by crimping them a little too much.Neck splits arn't such a big deal.CASE splits are a BIG deal as well as head/case seperation,,I might be wrong but I don't think so..

[WESHOOT2]

The Winchester Small Pistol Magnum primer has been tested (check your manuals) to add considerable pressure (up to 5K PSI) to Magnum handgun loads; I suggest testing with both CCI550s and Federal's 200.