Factory Ammo Over Pressure

[alfsauve]

(This isn't "handload" or "reload" as such but I we don't think we have a Factory Ammo forum.)

Was testing a number of loads yesterday in my 8-3/8" 686-_ and I wanted to see where Hornady factory ammo shot on target compared to my handloads. This is Hornady .357Mag 158gr XTP. #90562. (~1250fps @ muzzle) (My loads run the same velocity between ~1250 and ~1300fps depending on powder.)

In two rounds out of the five the primer flowed back into the firing pin hole and locked up the action.
This 686 has 1,000s of very hot .357 rounds through it (IMHSA) and I've never had this happen with reloads, much less factory ammo. Will be contacting Hornady before I shoot anymore of this Lot.

Not the best picture but the center two you can see the raised impression where the outer two just have the firing pin dimple.

 

[edwardware]

Based on my experience in .357, those primers don't look overpressured. I have factory and handload ammo that flattens the radius considerably more than that.

I say the cups are soft, and your FP hole is large.

And before the whingers arrive: yes, primer radius flattening is a very coarse way to measure pressure. It's also the only way available to us.

 

[troy fairweather]

just soft primer cups, those don't even look hot to me.

 

[drband]

Many firing pin holes are chamfered. Have you checked yours? Very common to cause what you’re seeing.

 

[Stubert]

Primers are not flattened, don't worry there fine.

 

[Fine Figure of a Man]

I agree they don't appear to be too hot.
Here is some 41 Mag brass from some warm loads. Primers flattened.

 

[alfsauve]

Just to be clear, we're looking at the center two cases.

Sorry, but I don't consider it fine when the primer flows back INTO the firing pin hole and locks up the action.

This is a stock 686 no dash that has been used with LOTS of hot loads and never has this happened before. (not yelling, I know reading this it seems I am.)

OKAY, OKAY, maybe I should have said in the title. "Over pressure or soft primer cups?"

So are soft primer cups normal for Hornady hunting loads?

 

[alfsauve]

Here's a better picture where you can see the difference. Notice the 2 on the left and the one on the right have a normal dimple. But there are the two where the primer is raised in the center, not dimpled.

 

[Fine Figure of a Man]

So are soft primer cups normal for Hornady hunting loads?

Maybe so and possibly thinner?
They look cratered but not flattened.
No experience with Hornady ammo, I don't think I have ever fired a factory round of any kind in .357

 

[alfsauve]

...
No experience with Hornady ammo, I don't think I have ever fired a factory round of any kind in .357

Until this month I hadn't either. But my loads (and the bullets I used) were for IHMSA. For silhouette shooting. I thought for hunting, I'd use some of the new technology bullets out there. Ran 10 Fiocchi hunting rounds no problem, but these were my first Hornady rounds.

 

[25-20 WCF]

Soft cups don’t explain why only some of the cartridges showed primer flow....unless they changed lots during the loading cycle. But it is possible, as is a faulty powder dispenser. A large firing pin hole doesn’t explain why only a few cartridges exhibit the extrusion.

Primer flattening is greatly influenced by headspace. Large headspace will let the primer back out, then the case comes back (as pressure starts to drop) with the result a “flattened” primer. High pressure doesn’t have to be the cause.

Bottom line - call Hornady ASAP.


.

 

[Hooda Thunkit]

S&W had/has a factory recall for the 686- no dash, for that exact problem.
I have a 686-M, the M being the factory mark for a no-dash that was sent back for the upgrade.

I would suggest contacting S&W ,they will send a call tag, and repair that revolver no charge, if it is indeed a 686-.

 

[CraigC]

A 158gr at 1250fps is not overpressure unless they used the wrong powder, which is unlikely. Either the primer cups are too soft or your firing pin hole is too large or a little of both.

Reading primers for pressure is for rifles.

 

[alfsauve]

Xx

S&W had/has a factory recall for the 686- no dash, for that exact problem.

Yes, my gun has the M stamp.

But out of thousands of rounds only these two have had the problem.

 

[jmr40]

That recall was 30 years ago. If yours has the M stamp that means a pretty old gun that was sent in for the recall. Out of those thousands of rounds it might be in need of another repair. I don't think you are over pressure either. I think it is a combination of several things all coming together at once. The original recall meant simply replacing the hammer nose bushing IIRC to a smaller one. Over time and use the hole may have enlarged.

 

[sequins]

The fact that you experienced a failure says it all- this ammo is unsafe.

Pull 5 rounds and gauge the powder, off a box of 50 10% is a good measure. I want to see the SD of the powder load- I expect to see a +/-2gn variation and i expect that to be your problem.

 

[243winxb]

I would guess Hornady ammo has a powder problem. Some with more then others. As said above.

But the firing pin needs to stay in contact with the primer after firing. The screw does wear. I would replace the parts if still using the originals.

Make sure the strain screw it screwed in fully and tight.

 

[skeeterfogger]

I would guess Hornady ammo has a powder problem. Some with more then others. As said above.

But the firing pin needs to stay in contact with the primer after firing. The screw does wear. I would replace the parts if still using the originals.

Make sure the strain screw it screwed in fully and tight.

View attachment 840554

Not same class of gun but I bought an 1858 rem na bp that was told sprayed hand and face when shot. Strain screw was so loose the hammer would fire but was floppy. Would not stay firm against nipple. Primer fragments and gas were flying out.

 

[Rule3]

By all means contact Hornady. Years ago I had problems with their Critical DUTY +P 9mm ammo. The cases would bulge (much like Glocked) when fired out of a SW Shield. At that time their ammo was loaded in Starline Brass. Anyway they sent a call tag, picked it up, did all kinds of scientific tests and the results were that SW shields had a poorly supported chamber. Anyway they still replaced the ammo and sent me a ball cap.

Yes, the Starline warning is due to this.

https://www.starlinebrass.com/brass-cases/9MMP-Brass/

 

[alfsauve]

The ammo is back at Hornady. Awaiting their inspection report.

I discovered I had another box (20rds) of the same lot #. What the hey. Hold my beer.

I chrono'd 6 rounds (small sample I know) and it was right on with what they say on the box. Got to hand it to them on that. No inflated velocity figures. Average was 1252fps (LabRadar V0) out of my 8-3/8" 686. I shot all the other rounds later in the range session with no problems. All primers looked like they should.

 

[Innovative]

alfsauve . . . .

One of my customers recently had the exact same problem that you described, and it also happened with his S&W 686 (6" barrel). My pictures (below) show a much better view of what you experienced. Hornady will test your ammo and tell you the pressure is "within specifications", and they'll send you a replacement box of ammo.

Very few rounds had the symptom you described, and the rest looked fine. None of the primers showed high pressure (flat primers). I found that the problem was caused by the cylinder timing being set extremely close, and two chambers were not well aligned with the barrel. Have your gunsmith verify chamber alignment with a range rod, and it's an easy job to adjust the individual timing of each chamber.

I'll bet you'll find the same thing I found.

 

[alfsauve]

I found that the problem was caused by the cylinder timing being set extremely close, and two chambers were not well aligned with the barrel.

Thank you, Larry, for the much better picture.

Interesting. And I won't discount the problem is with my gun. I can see how if the cylinder isn't aligned there would be higher pressure getting the bullet into the forcing cone at an slight offset. I may take it to my revo smith and ask him to check anyway to cover the bases. Or maybe just go ahead and have a new hand installed and timed.

My question is why just an odd one or two rounds of Hornady ammo having this problem? Did you ever see any other brand ammo have this problem? Yours was 125gr and mine was 158gr, but both Hornady. Why wouldn't this be an issue every time around that chamber came up? Or is the timing right on the cusp so it only fails on rare occasions?

 

[edwardware]

. . . it's an easy job to adjust the individual timing of each chamber.

I have to ask. . . how?

Unless you fit a wide stop through the frame window and then recut all six notches, I'm not seeing how, and that's not easy by any stretch.

 

[Zendude]

Maybe inconsistent primer cup strength with the Hornady ammo? Or maybe the rim thickness was thin (increasing headspace) on the Hornady brass that showed the symptoms?

 

[alfsauve]

So just to conclude this thread. I got a replacement box of ammo on Friday. No particular explanation. Took about 6 weeks all told. So that's that.