Flattened Primer Question


September 17, 2007, 06:48 PM
I was testing a 9mm 115 FMJ load using Titegroup 4.6gr. 1.136 oal CCI small pistol primer and all the primers was flattened. The maxload for 9mm in Titegroup is 4.8gr. Additional information: I'm shooting it from a XD9 Tactical, I weigh the powder with RCBS 505 scale, my oal was was +/- .003", the weather was in the 60's and these were the only batch I fired from my XD9. So what did I do wrong?:confused:

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September 17, 2007, 07:51 PM
My understanding is that "max recommended load" means that the manufacturer is only swearing that on THAT day, in THAT barrel, at THAT air temperature it was a good idea.

Are you completely sure that your scale was accurate?
Did these primers show up at the end of a long string of firing so that the chamber was maybe too hot, thus locking things up just a tad too long?
Can you confirm that the OAL was correct?
Any particular extremes to your local air temperature?

Just a start to the thought process....

September 17, 2007, 08:09 PM
Those dont look to bad . Try pushing a 40 grn Vmax to 4200 fps out of a 22-250 , THATS a flat primer !!!

Just back it off .1 or so . NavArch brings up some good points !!!!

September 17, 2007, 09:22 PM
It has been my understanding that a "flattened primer" exhibits no bevel around the edges, that the heat and pressure has essentially softened the primer metal and reformed it in the case cup. The image, while not the best focus (macro mode would have been better), it looks to me like a bevel around the edges still exits. When my cases come out like this, I consider it an OK load.

Any informed reloaders that know what they are talking about please express an opinion.I am not any kind of expert, just expressing how I've been looking at the topic of "flattened primers". I'd sure like to know the real skinny on the subject.

September 17, 2007, 10:01 PM
ditto on hook686, the loads appear to be warm, but not excessive. I noticed irregular shapes when the primers flow from excessive pressure. Change primers brands and see what happens. Some are softer than others for standard primers.

September 17, 2007, 11:07 PM
He might be confusing cratered firing pin strikes with flattened primers. The primers don't look bad to me, still see a clear radius on the primer all around the primer pocket. However if his gun doesn't crater the primer on factory ammo, I'd back off a bit just to be safe.

One other point, the max load is usually listed using a specific brand of brass, bullet and primer, different brands of brass may have smaller capacities requiring lower maximum loads, different bullets and different primers may change pressures too.

I rarely push max loads, prefering to stay mid range so I don't really need to worry about what brand of primer I can find when I need more or worry about sorting case head stamps.


September 17, 2007, 11:26 PM
But take a look at the primers in this link:


FWIW, I think the order of firing of the primers was 1-3-2-5-4. Note there's no leakage, and IMO, hardly any flow. Those primers were the results of 17-18-gr. of AA#7 in a 38+P case under a 140LTC bullet. A cylinderful, as pictured, was fired--that's a S&W 640 (SS) pictured. While the recoil was 'massive,' I have felt worse with the 357 125 hotrod loads.

Two of the cases extracted fairly normally--the last three became progressively more difficult, with the head separation occuring as I gently tapped on the case with a range rod. Yes, the charge was an 'accident,' NOT a double charge. It filled the case, and was slightly compressed.

A Quickload post-event calculation showed the pressure was something between 55,000 and 72,000.

I no longer read primers like tea leaves.

Jim H.

The Bushmaster
September 17, 2007, 11:49 PM
Forget the flattened primers...Incidently, actionflies, yours aren't that flattened. They have nothing to do with determining pressure. Only if you note cratering, soot at the edges of the primer pocket and the primer, cases that extract hard or punctured primers.

All flattened primers mean is that the primer backed out just before the case had a chance to expand against the chamber wall and was slammed against the breach and reseated, thus flattened...

September 18, 2007, 04:55 AM
Primer appearance only means something when making comparisons and keeping track. Sometimes flattened primers means the primer was seated a bit hard - a good reason to clean primer pockets. Basically, a good bevel around the firing pin indent is good. Actionflies, your firing pin seems to be 'dragging' during ejection. Have you determined the minimum load your pistol requires to cycle reliably?


The Bushmaster
September 18, 2007, 09:44 AM
peterotte...Glocks usually make that mark on the primers. Even my Firestar will, on occasion, make that "drag mark"...No biggy

September 18, 2007, 02:45 PM
You're right, Bushmaster, my model B did that all the time. I was wondering, however, whether that could be a sign of overvigorous slide recoil? I've never heard of it being a problem, but it could mean room for reducing pressures if so desired.

I do seem to remember a smithy saying that a dragging firing pin could also indicate the primer being pushed onto the firing pin enough to grip it, in the case of an inertial firing pin. I know my pin was too long.


September 18, 2007, 10:32 PM
How many reloads do you have on those cases? I was thinking the primers were backing out, as there is not really any cratering. One of the reasons a primer backs out is a loose pocket in stressed (shot too many) brass. If these have 6-8 stout loads on them, it might be about time to cycle them out. Also check to see if your cases are proper length. If they're too short, you'll headspace too deep into the chamber and the case will have to jump a long way before it stops, giving the primer time to escape some.

Noah Zark
September 24, 2007, 08:50 AM
I have a favorite 9mm load using W231 and 115 gr plated lead bullets and while it doesn't flatten primers in my BHPs, Beretta 92F, or HS2000, it will flatten them like a mother in my S&W 76 and Sterling Mk4 subguns.


September 24, 2007, 09:00 AM
Look pretty normal to me. Nothing to worry about. :)

Mal H
September 24, 2007, 09:55 AM
"So what did I do wrong? :confused:"

As most have already said, nothing.

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