This Win SPM was fired with a 125g XTP and max load of 2400 (17.7g per Lyman 3rd). Interested in any comments for our education.

One question I would have: Do magnum primers accept higher pressure than standard primers?

(I know I don't need a magnum primer for 2400, just using them up to save my SPP.)

Attached Images

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Looks like you’re getting extremely high pressure causing the metal to flow into the firing pin opening. I’d take this as a danger sign. I could be wrong but this would send up a red flag to me.

This can be a LONG conversation.

98% of the time I scoff at folks who attempt to read primers like tea leaves. Your picture is, however, outside the normal. My knee jerk reaction is to ask if you launched these from a 686 no dash or dash-1 “pre-M Stamp” because this one really does appear as if it’s attempting to flow in to the firing pin bushing and that is a well known issue of the earliest L-frame revolvers.

Yes, a magnum primer is supposed to have a thicker cup, more resistant to pressure. However across differing brands, there is no agreed-upon spec.

Back on the subject of “reading” primers, it has been my experience that the look of a fired primer is irrelevant unless/until you can show pictures of:

same brass
same primer
same bullet
same powder of increasing charge weights
all fired from the same gun/same day

That’s a more clear way of suggesting that one perfectly safe/good load with a 158gr and Accurate#9 and another one with H-110 and 125gr JHP have no relationship to each with by the appearance of the fired primer.

(Except of course if the primer pierces or leaks, which is BAD and dangerous)

In general, yes. Mag primers may have thicker cups..

But 2400 & WSPM do raise the pressure to dangerous levels, as your primer is showing.

See pressure test data- Test of Hercules vs Alliant 2400 in the 357 Magnum with 6 different primers

It's way too much pressure for the primer you are using, it may or may not be a lot of pressure for the gun.
As has been pointed out, magnum primers are supposed to be able to take more pressure but there is a lot of variation by brand.
How are you set for SRP?

My first thought is that there is something wrong with the OP's gun; namely the firing pin hole is over-sized.

Do the primers of other fired magnum casings look similar?

Reading primers can be useful . Position sensitive powders can create pressure problems, or squib loads.

High magnification helps

This lot of powder is on the HOT side? The Hodgdon Data 158 gr lswc bullets is very different then mine. Bevel vs flat. Bearing surface.

Hodgdons start load should not blank a primer, even with a 6 gr weight bullet difference.

Photos- S&W M28-2 357 High Pressure, Locked Action | The High Road

Have a great 4th.

Would be interesting to see a photograph of the breechface, and specifically, the hammer nose bushing.

__________________
Ret. LE, FA Instr, S&W Armorer

hi do not think this load is hot. the primer did not even flatten out in the pocket, primer is still round....dan

I don't believe your WSPMs are seeing the pressures my WSPMs are. I would consider extraction, and velocity comparisons while forming your opinion.

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Suggestion ONLY: by reducing your stated MAX load you may find no reduced effectiveness for the load and no such irregularities...?

I have never seen nor experienced a primer that looked like that: mayhaps a SS pin, a defective case, primer, etc., ... WHO KNOWS?

Why would anyone wish to expose themselve to a potentialy fatal recurance?

One might reassess one's loading priorities...?

Cheers!

Did you start right out at the MAX load out of the book with your reloading
and this is the result?

Or did you work up gradualy to the MAX load listed and at that point the issue showed up..

I'd back off the MAX load. It simply looks a bit too much pressure for the particular case, primer, bullet combination.
Components vary.
Work up to the MAX load gradually and watch for such signs to appear and then back off.

I would back off a half grain and see what happens. I have pushed loads to the point of piercing primers and splitting cases before I caught it.

Yikes!!!!!!!!! looks like the moon. Mike, any higher and you'll be in the ER with a Team picking steel out of your face and hand. You need to reduce that by 10% Min and inspect the weapon you stressed out with that load. Last time i saw someone shoot ammo that hot was the French Police Armorer doing a annual inspection and proof test on MR 73 service revolvers.

A lot of good input here, thanks.

This was a current max load from Lymans 3rd edition, with a Hornady XTP 125g, so I was using the exact bullet etc. I’ve also tried a couple other powders similarly, but never with this kind of primer deformation. This load had more kick than the others too.

For the curious, this was fired in a CBC break-open with an 11” 357 adapter. So the firing pin setup is not optimal for this kind of pressure. As SW Dan noted, no flattening. Kind of a curious thing.

A good learning experience, and I’m going to creep up on that edge a little slower from here on.

I would love to see what the end of that firing pin looks like..........
as well as the Dia. that it measures out at.

I would suggest an issue with the pistol. The outside radius of the primer is still very much there. Too much so for this kind of flow into the firing pin bushing/hole IMO. If this is a frame mounted pin has it been changed to a non OEM with a nose profile/size that is off just enough dimensionally that this is occurring at max pressures?
I also switched to Fed 200 SR primers years ago for all my full house .357 loads

An 11" 357 Magnum adapter in a CBC break open...

Now, THAT'S the ol' horse of a different color in a fine kettle of fish...!