[Significent]

I just looked at the spent primers I took out of some Georgia Arm Canned heat (reloads). I'd say they were flattened showing signs of over presurization. Can some some confirm my suspicion?

http://members.cox.net/thartle/SpentPrimer.jpg

Thanks!

[P95Carry]

My own 0.02? This pic is not in itself quite enough.

It appears that there is ''flow'' which could be ascribed to a generous area of chamfer in the primer pocket - so the primer expands to fill that space. There is no view here to see the nature of the area around pin strike ........ if some bad flow there, then probably some over pressure.

I personally expect some flattening ...... in as much as ... at moment of pin strike and then ignition, there is and must be some primer ''set back'' ...... the primer tries to start coming out but is whacked back in at that time.

If the process is too violent then often the metal will start to flow around the firing pin ... that I do not want to see. The flow here tho if due to pocket chamfer, would not in itself strike me as definite over pressure.

My .357 mag case primers usually get pretty flattened but the loads are hot ... but they don't show flow round the pin .... plus, they are within loading limits anyways.

[Significent]

P95Carry:

I'm not sure what to look for in the way of primer flow around the firing pin strike. It looks pretty normal to me. There is a very, very slight ring around the perimeter of the strike, but I don't think it's significant. Anyway, the cases look perfectly fine. Maybe I'm just being paranoid.

Thanks for your help.

[P95Carry]

Tell ya what .......... paranoia is way better than compacency .. every time!

I haven't a pic ... unfortunately ....... but hang on ...... OK a quick diagram for you. The left profile is ''normal'' and the right is cratered ... with raised edges ....... that is what I would wish to always avoid. Hope that helps some.

http://www.patriotnetwork.net/cb_gun/primer_bulge.gif

[Clark]

http://glocktalk.com/attachment.php?s=&postid=926833

[HSMITH]

MANY factory loads flatten the primers. Flat primers are only one indicator of pressure and a poor one at that. Primer cup softness is widely varied by brand, if your picture is a winchester or a federal it is pretty normal, if it is a CCI the load is approaching warm. Primer condition unless cratered is only a ballpark indication, you need to look to other signs like extractor marks and breech face printing or sticky extraction and things like that.

[P95Carry]

What was the ''history'' behind the one on the right Clark??:eek:

[Significent]

I'm using Winchester primers. None of my strikes look like anything in Clark's photos. The raised ring around my firing pin strike is only barely perceptable. I've had no problems extracting brass. I guess I'll keep shooting them. Thanks for your insights!

[Significent]

I grabbed a bunch of fired brass to see how the primers compared. The primer on the left is an example of the worst. The one on the right has the least noticeable ring around the strike. Both look a little more exagerated in the scan than they do just looking at them.
http://members.cox.net/thartle/PrimerStrike2.jpg

[P95Carry]

Definitely some cratering there ....... on left one it is enough to make me wonder a bit .... tho as someone else mentioned - HSMITH - as this is Winchester primer ... maybe not too much concern.

If CCI which is harder metal then I would be sufficiently concerned. Strange thing is ... primer set back after ignition tends to flatten out whole surface .. i wonder sometimes as to how the cratering survives the set back (and thus flattening) process. It is almost like it occurs just after set back........ tho it should be an almost instant effect immediately on ignitioon as pressure peak reached.

Anyways, I doubt that is too bad .. i don't think tho you mentioned (I may have forgotten) .... just what this load is ....... am I assuming correctly this is .308 brass? headstamp not too informative.

~~~~~~~~~~~~~~~~~~~~~~

On reflection I recall you mentioned .223 .. so these could be 5.56 cases then. Quite a high pressure round at factory levels anyways.

[Significent]

You're right. They're 223 Remington. I mentioned this in the other thread about hand priming that I opened. Thanks again for your help.

[ambidextrous1]

Thanks for your comments, P95.

Here's a theory on cratering during setback: The primer metal flows into the firing pin clearance hole, and will do this with or without setback, if the loads are hot.

The fp clearance hole must be significantly larger than the firing pin diameter, by .010 to .015 inch, to ensure function when the area is loaded up with combustion residue.

That's my opinion - but what do I know?

:rolleyes:

[P95Carry]

Ambi .. I had considered the clearance for pin ... and on further thought guess you are probably right on that ... only explanation really and logical.