Primer Maximum Acceptable Depth

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Hartkopf

Hartkopf

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I always shoot for .003 to .005 below flush just like the Lyman manual says.

Just curious how far below flush has been successfully shot.

After a member her mentioned a problem in another thread, I was very surprised to find some factory 40 S&W defense ammo with the primers between .006 and .010 below flush.

Most everything I shoot is out of a Glock and I’ll be testing with the lowest primers first to use them up, if they’ll fire. Would you reject the .006 cartridges or call it close enough to spec? I’m not in dire need to use this ammo, only curious what you guys have been able to successfully fire.
 
I had some RP .25-06 brass with primer pockets so deep that a bottomed primer was out of reach of the bolt action's fixed firing pin protrusion. Primers seated flush fired but accuracy wasn't great.

A .010" primer sounds deep for a fixed protrusion striker. A 1911 wouldn't care.
 
Hartkopf said:
I was very surprised to find some factory 40 S&W defense ammo with the primers between .006 and .010 below flush.

Would you reject the .006 cartridges or call it close enough to spec? I’m not in dire need to use this ammo, only curious what you guys have been able to successfully fire.
Click to expand...
While I usually aim for .004" below flush, I tested different primers to .008" below flush and they all went bang - https://www.thehighroad.org/index.p...ts-your-experience.630512/page-4#post-7810685

You will often find factory primers to be seated deeper than .004" below flush.

index.php
 
With my bench mount I can keep it pretty consistent. But with my hand primer which I used for many tens of thousands of rounds and still do if Im loading rifle or off my progressives, many of the primers set well below flush. They bottom out and get smashed a little as well. I never had one fail. Probably half was fired in a Glock. I worry more about high primers than low.
 
The primer should be seated at least deep enough so that the anvil has touched bottom, but should really be deep enough so the cup is pushed down over the anvil most of the way or to the bottom of the primer pocket. We don't want to push it any deeper than having the cup touch the bottom of the primer pocket (crushing the primer), but can get away with some of that. Most primer issues are from not seating deep enough.

We accomplish this as close as we can by feel and measurements. It might be .004 deep, it might be .006 deep, maybe even more. It's one reason why I use primer pocket uniformers on match rifle ammo, it makes it easier to have primers uniformly seated using an adjustable priming tool with a positive stop. They need to be seated consistently.
 

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According to SAAMI, the depths for large pistol primer pockets are .118" to .122", large rifle primer pocket depths are .128" to .132".

My 45 ACP shotshell rounds all use rifle cases and they always go bang. If everything is in tolerance would be a .006-.014” difference between seating a LPP in a pistol pocket vs rifle one.

I don’t seat them to a depth but until they are seated. I might ask the other part of the equation, if your primers are fully seated and not being ignited, what is your firing pin protrusion?
 
Been using a hand primer since the early 80's. I never worry about it. It never made any difference in all of my match loads. Sometimes you can over think reloading.
 
frankmako said:
Sometimes you can over think reloading.
Click to expand...

I share that sentiment very often. I often have to explain why things bench rest and chassis rifle shooters do aren't really necessary when loading handguns. Many of the expensive and time consuming things done folks do didn't give me enough (or any) improvement even in my 1k yard guns so I don't stress many of the things people stress over
 
My bud has one of the RCBS priming tools that sits on the bench and has a handle out to the side. Lots of leverage. He loaded some 270 rounds and started having misfires. The primers were obviously deep and seated too deep for his rifles firing pin protrusion.

One of these. https://www.midwayusa.com/product/1012932670

I use a Lee hand priming tool and always get them below the case head and have never had a high primer like I would sometimes get when priming on the loading press. The loading press works fine as long as I am paying attention to the job. A handgun (auto) seems to have an almost unlimited amount of firing pin reach and you can get away with deep seated primers.
 
Just to verify I’m thinking of this correctly, we would need to add the head space distance to the primer depth to know how far the primer could possibly be from the breach face?
 
Hartkopf said:
to verify I’m thinking of this correctly, we would need to add the head space distance to the primer depth to know how far the primer could possibly be from the breach face?
Click to expand...

Or extractor claw on most guns. Often they hold the round short of the case mouth
 
Hartkopf said:
Just to verify I’m thinking of this correctly, we would need to add the head space distance to the primer depth to know how far the primer could possibly be from the breach face?
Click to expand...
Yes. For a cartridge that head spaces on the case mouth. Unless forward movement of the round is stopped by the extractor.

Head clearance (headspace) can be as much as .015"
 
Walkalong said:
The tolerances on primers and primer pockets show us why we can't just seat to a certain depth below flush in all cases
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Not to mention primer pockets that were "modified" and made deeper by reloaders.

For these reasons, especially when hand priming, I look for the initial resistance of primer anvil feet hitting the bottom of the primer pocket but continue until I feel the secondary resistance of anvil sliding into the primer cup and pre-load on the priming compound.

Depending on the primer pocket depth, just seating to flush may not ensure ignition of primer.

Here's US Army AMU's take on primer seating depth - http://bulletin.accurateshooter.com/2016/01/primer-seating-depth-uniformity-and-accuracy/

"Here at the USAMU, we ensure our rifle primers generally run -0.003″ to -0.005″ below the case head. Maximum primer depth is -0.006″ and minimum is -0.002″."
 
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Hartkopf said:
Just to verify I’m thinking of this correctly, we would need to add the head space distance to the primer depth to know how far the primer could possibly be from the breach face?
Click to expand...
Head clearance, but basically yes.
 
LiveLife said:
"Here at the USAMU, we ensure our rifle primers generally run -0.003″ to -0.005″ below the case head. Maximum primer depth is -0.006″ and minimum is -0.002″."
Click to expand...
Can't argue much with that, except to say I'm more comfortable with a minimum of .003.
 
Hartkopf said:
Just to verify I’m thinking of this correctly, we would need to add the head space distance to the primer depth to know how far the primer could possibly be from the breach face?
Click to expand...
Kinda Hocus Pocus really, IMO just seat your primer fully without crushing,
Fully fire form your brass to a heavy bolt lift then bump the shoulder a couple thousand or free chambering. Tighten your die lock ring and repeat.
KIS
YMMVBTM:cool:
 
My problem is the opposite. I find that on .45 ACP my primers are a little proud, especially Wolf primers made in Russia. They work fine in .38 Spl's. I know primer depth is important but is there a danger on having proud primers? I never had a problem firing those rounds.
 
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