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Notes on "Pierced" Primers

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denton

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pierced primers.jpg

These are 223/5.56 cases from an AR15.

The left two cases were from a 25 grain load of AA2520 with a 62 grain bullet. The firing pin dent looks pretty normal.

The middle two cases were from a 26 grain load. The firing pin dent has started to flow back to flush.

The right two cases were from a 27 grain load. The firing pin dent has flowed back out, inverting itself. In the lower case, the bulge is still attached. In the upper case, it has fractured around the base of the bulge, leaving a hole. The broken off bulges can end up in the rifle's mechanism. I've had that happen.

CCI magnum primers fixed the problem, since they are thicker.
 
Thank you for the visuals. I looked up the Western Powders load data for AA2520, and I see that 27 grains is above maximum. So it shouldn't be a surprise that the primers failed. Why would changing to CCI Magnum primers be any better? Just because they are thicker doesn't matter, the load is still above max.
2520 Load detail.png
 
Zahn said:
Thank you for the visuals. I looked up the Western Powders load data for AA2520, and I see that 27 grains is above maximum. So it shouldn't be a surprise that the primers failed. Why would changing to CCI Magnum primers be any better? Just because they are thicker doesn't matter, the load is still above max.
View attachment 988738
Click to expand...
Scroll down to the 5.56 data. 27 grains is not above maximum. 27.5 is the listed maximum.
 
Zahn said:
Thank you for the visuals. I looked up the Western Powders load data for AA2520, and I see that 27 grains is above maximum. So it shouldn't be a surprise that the primers failed. Why would changing to CCI Magnum primers be any better? Just because they are thicker doesn't matter, the load is still above max.
View attachment 988738
Click to expand...
62 gr 2520.png
According to this, 27.5 grains is maximum IF YOU ARE USING MILITARY M855 PROJECTILES.
All rifles are a little different and yours may be hitting maximum pressures before the mfr's test barrel did. Also, I have seen references in other places that AA2520 can be temperature sensitive.
Regardless, one shouild start at the starting charge and work up to maximum and stop there.
 
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Poper said:
According to this, at 27.0 grains of you are 113% of the maximum load. Anytime a body exceeds the maximum powder charge, he should not be surprised when bad things happen. I will postulate that if you continue to run over maximum powder charges through your rifle, you will likely begin to suffer serious damage to said rifle, if not a catastrophic failure. It is just a matter of time.
Click to expand...
Not really. The maximum load for 5.56 is 27.5 grains, so 27 grains is 98% of a full load, not 113%.
 
Addendum, instead of editing my prior post. Doesn't the 556 load call for Mil-Spec primers? I see the Western Load Data calls out WSR, which also has the thicker cup if I remember correctly.

Again, this goes back to working up your loads incrementally. Even brand and type of primer (Magnum or #41 vs regular SRP) factors into what is safe.

Denton, I meant it when I said, thank you. This is a valuable reminder.
 
Zahn said:
Addendum, instead of editing my prior post. Doesn't the 556 load call for Mil-Spec primers? I see the Western Load Data calls out WSR, which also has the thicker cup if I remember correctly.

Again, this goes back to working up your loads incrementally. Even brand and type of primer (Magnum or #41 vs regular SRP) factors into what is safe.

Denton, I meant it when I said, thank you. This is a valuable reminder.
Click to expand...
Yes, you are correct that the military primer is designed for the 5.56. It has the same thickness cup as the CCI Small Rifle Magnum primer, and the same power.

The military primer has a bit more space between the cup and the anvil than the magnum model.

I think that one contributing factor in my AR is that (with no clear plan or reasoning) I replaced the steel firing pin with a titanium one. That gives a little less inertia holding the floating firing pin against the primer.
 
denton said:
Not really. The maximum load for 5.56 is 27.5 grains, so 27 grains is 98% of a full load, not 113%.
Click to expand...
If 5.56 NATO and not .223 Rem. data, then yes, 27.5 gr. is max. with the M855 projectile only. Anytime we substitute a component, be it primer, case or bullet, the load should be redeveloped from starting charge to maximum charge or signs of excessive pressure, whichever comes first. There are no guarantees any particular gun will be compatible with maximum powder charges.
 
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Accurate 2520:
"Accurate 2520 is a medium burning, double-base, spherical rifle propellant designed around the 308 Winchester. 2520 is a common Camp Perry powder and is extremely popular with many service shooters. 2520 also performs extremely well in 223 Remington with heavy match bullets (62 to 80 grain). This versatile powder has superb flow characteristics and is well within the threshold limit for the M14 systems".

Did things change because of the thicker cup? The CCI 450 Magnum primer has about a 0.005" thicker cup or did things change because of going to a magnum primer with a spherical powder?

Speer in their Number 12 reloading manual suggested the use of a magnum type primer with all flake or spiracle powders. That changed in their Number 13 manual. However, there is no shortage of references to using magnum primers with flake or spiracle powders.

As to the CCI #41 primer.

Small rifle primers
#41......................................Mil. Spec. primer, thick cup, magnum primer charge, angle of anvil change.

The above from CCI. The sensitivity is a function of anvil angle and thick cup but the cup is no thicker, about 0.025", than a CCI 450 Magnum primer.

Ron
 
Poper said:
View attachment 988741
According to this, 27.5 grains is maximum IF YOU ARE USING MILITARY M855 PROJECTILES.
All rifles are a little different and yours may be hitting maximum pressures before the mfr's test barrel did. Also, I have seen references in other places that AA2520 can be temperature sensitive.
Regardless, one shouild start at the starting charge and work up to maximum and stop there.
Click to expand...
I'm more than a little bit familiar with the 5.56 cartridge and projectiles, having been hired by the operator of Lake City Army Ammunition Plant as a consultant, and successfully resolving a major production issue with the M855. As part of one of our tests, we fired thousands of rounds with the ammunition and rifle at 150 F, and even some above that.

It's not a matter of too much pressure in the cartridge.

It's a matter of starting with a primer that is only suitable for 223 level pressure, and finding that as I increased the charge, I really did need to switch to something more like the military primer.
 
Reloadron said:
Accurate 2520:
"Accurate 2520 is a medium burning, double-base, spherical rifle propellant designed around the 308 Winchester. 2520 is a common Camp Perry powder and is extremely popular with many service shooters. 2520 also performs extremely well in 223 Remington with heavy match bullets (62 to 80 grain). This versatile powder has superb flow characteristics and is well within the threshold limit for the M14 systems".

Did things change because of the thicker cup? The CCI 450 Magnum primer has about a 0.005" thicker cup or did things change because of going to a magnum primer with a spherical powder?

Speer in their Number 12 reloading manual suggested the use of a magnum type primer with all flake or spiracle powders. That changed in their Number 13 manual. However, there is no shortage of references to using magnum primers with flake or spiracle powders.

As to the CCI #41 primer.

Small rifle primers
#41......................................Mil. Spec. primer, thick cup, magnum primer charge, angle of anvil change.

The above from CCI. The sensitivity is a function of anvil angle and thick cup but the cup is no thicker, about 0.025", than a CCI 450 Magnum primer.

Ron
Click to expand...
I was mainly concerned with the primer bulge breaking off, leaving a "pierced" primer and a stray piece of metal in my rifle. All I changed was the primer... thicker cup, hotter charge. That fixed the problem. Regular primers really are not optimum for the AR15 and for 5.56 level pressures.
 
denton said:
I'm more than a little bit familiar with the 5.56 cartridge and projectiles, having been hired by the operator of Lake City Army Ammunition Plant as a consultant, and successfully resolving a major production issue with the M855. As part of one of our tests, we fired thousands of rounds with the ammunition and rifle at 150 F, and even some above that.

It's not a matter of too much pressure in the cartridge.

It's a matter of starting with a primer that is only suitable for 223 level pressure, and finding that as I increased the charge, I really did need to switch to something more like the military primer.
Click to expand...
Agreed. Whenever a substitution is made (say Sierra 62 grain Game King for M855) then one should retrace his steps and start at the begining. The OP does not state his projectile, only the weight. Not all 62 grain projectiles are identical and the exact geometry can differ considerably.
Not all guns will perform exactly the same. IMHO, starting out at the maximum or near maximum powder charge, is asking for trouble.
I hope this is helpful.
 
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This is a very timely discussion. With all the shortages, we don't have the luxury of selecting primers. I know that I buy when something is available. So I have CCI 400 on hand. I also have some WSR, which is slightly thicker according to Internet sources at .021" instead of the .020" of the CCI 400.

I will progress through my load workup very slowly.
 
denton said:
I was mainly concerned with the primer bulge breaking off, leaving a "pierced" primer and a stray piece of metal in my rifle. All I changed was the primer... thicker cup, hotter charge. That fixed the problem. Regular primers really are not optimum for the AR15 and for 5.56 level pressures.
Click to expand...
Oh I agree and went with the CCI #41 and #34 years ago. Just can't help but wonder was it the thicker cup or magnum priming that made the difference. The far right primers in your image also lead me to wonder how much room the firing pin has?

"Blueprints call for a 0.058-inch-diameter firing pin hole. If the hole is bigger than that, then the primer gets weaker and weaker in its puncture resistance, aka: pierced primer". Then too the loads were not exactly start loads. :)

Ron
 
Reloadron said:
Oh I agree and went with the CCI #41 and #34 years ago. Just can't help but wonder was it the thicker cup or magnum priming that made the difference. The far right primers in your image also lead me to wonder how much room the firing pin has?

"Blueprints call for a 0.058-inch-diameter firing pin hole. If the hole is bigger than that, then the primer gets weaker and weaker in its puncture resistance, aka: pierced primer". Then too the loads were not exactly start loads. :)

Ron
Click to expand...
OK, I think I understand a little better.

I'm pretty sure that the difference was the thicker cup.

Not shown in the picture are primers at lower loads. In those, the primer dents are really perfect.... no ridge. Also, with the thicker cup and 27 grains, the primer dents look right. So I think the pin to hole fit is OK.
 
denton said:
OK, I think I understand a little better.

I'm pretty sure that the difference was the thicker cup.

Not shown in the picture are primers at lower loads. In those, the primer dents are really perfect.... no ridge. So I think the pin to hole fit is OK.
Click to expand...
It is interesting looking at the progression with the load increase. Thanks for sharing the image.

Ron
 
When I 1st started reloading 223, not 556, I bought mostly CCI 500s. That was before I read of the cup thickness difference. I never did get any slam fires or pierced primers, thankfully. But I hardly ever go to max load and always do work up loads.

Now I mostly use WSP or Rem 7 1/2s for 223s. I still don't haven't loaded any 556 loads. Though I may have gone to the higher pressure by using a different headstamp. They were very flattened, but no cup flow. Those were Rem 7 1/2. I still need to pull the rest of that load.

All the CCI 400s are reserved for 300 Blk.
 
denton said:
View attachment 988732

The right two cases were from a 27 grain load. The firing pin dent has flowed back out, inverting itself. In the lower case, the bulge is still attached. In the upper case, it has fractured around the base of the bulge, leaving a hole. The broken off bulges can end up in the rifle's mechanism. I've had that happen.
Click to expand...

That is the primer anvil extruding itself through the hole in the primer!
 
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