Perforated primer cups??

[ThumperACC]

Hi All,

Lately I've noticed a few (maybe 5-10%) of my .223 rounds will have a hole in the primer cup (light shines through if you look carefully) after the round has been fired in my AR-15.

I load according to the following:
55 gn FMJBT bullet
25.8gn Accurate #2230 powder
CCI400 Small Rifle primers
Cart OAL 2.215"
Average Velocity 3088 fps

Now, I've only noticed this lately ( I recently bought a new batch of primers and I also recently got a Dillon 550B, so I've gone from hand priming to priming on the press and have had some minor issues with priming on the press).

So:
- Is this an issue I should be concerned with (like will it burn my firing pin over time)?
- What is this a symptom of (too hot of a load?, Primer not fully seated?, something else?)?

Thanks,
ThumperACC

 

[rfwobbly]

You're correct, that's not a good thing.

First thing to check is your primers. Several makers offer a "mil" primer that is slightly thicker than the standard small rifle for use in AR type guns.

 

[Ret.CWO]

Try using CCI Small Rifle Military Primers #41 that should solve your problem.

 

[weeniewawa]

if you say you have been having problems with priming on the new press that is where I would look at first

I think on the Dillon there is a way to adjust the depth of seating primers, may not be seating them all the way

 

[bigedp51]

1. As stated above check for defective primers (recalls)

2. check the firing pin tip for proper shape (not sharp or has the tip flattened or broken off.

3. Rifle head space set too long.

4. Over resizing your cases creating too much head gap clearance or "air space" between the bolt face and the rear of the case.

5. Weak firing pin spring.

Note: Your reloading and full length resizing your cases, my money is on the case being too "short" in your chamber from pushing the case shoulder back too far. (creating excess head space or head gap clearance)

3 and 4 cause the firing pin to turn into a cookie cutter and actually punching a hole in the primer. After the firing pin hits the primer, the primer is forced back "over" the firing pin and into the bolt face.

Please watch the animation below, and how the primer moves when fired. The first thing that happens is the force of the firing pin drives the case forward as it strikes the primer. Then chamber pressure pushes the primer "BACK" into contact with the bolt face. If the head gap clearance is too great the action of the primer being pushed back against the bolt face causes the firing pin to punch a hole in the primer.







Ok, I'm 60 years old and using a 100 year old rimed .303 British cartridge as an example, big deal BUT you have a .22 caliber mouse gun made by Mattel. (term used during the Viet Nam war for the M16, also called the South East Asian War Games) USAF 69-73 MAC You call, we haul.

Again you can see below how excess head space or head gap clearance can cause a pierced primer by the primer pushing a hole in your primer



Trust me, two five gallon bucket of .223/5.56 used in a bolt gun with .002 head gap clearance that does't throw my brass away.

 

[bigedp51]

How to stop over resizing your brass and pushing your case shoulder back too far.






Hint, hint, wink, wink.

 

[ThumperACC]

Thanks all.

Big Ed, I think you've nailed it. I recall when I set up the sizing die in the new Dillon press, I was looking for evidence of setting back the shoulder to know I'd set the die 'low' enough in the tool holder. Looks like I need to look at that, I must be making the cases a little short. Might be time to invest in a case gage.

My primers look exactly like the black and white photo in the clip you posted.

By the way, I like the shims you posted, unfortunately the die lock rings on the Dillon do not have a set screw (they're intended to be installed in a removable toolhead and never taken out so repeatable installation is not a needed feature).

Thanks again everybody,
ThumperACC

 

[gamestalker]

Are there any other indications of a problem, such as stiff or difficult extraction. The rounds that have the punched primers, do they chamber with little or no resistence after having been fired and before resizing. I've punched a few primers over the years, but it was always due to extreme high pressure. How does the OAL your seating at compare to the published OAL for the same bullet being used, is it longer or shorter than published SAMMI data? If your OAL is shorter than minimum published OAL by a pretty good degree, say .010" or more, it's very likely it may be a high pressure problem resulting from the seating too deep. In general, for each .001" deeper than published SAMMI data equates to approximately 1000 psi and as it gets deeper that generalized increase in cup begins to climb to more like 2000 or 3000 cup per .001". Although I am aware that punched primers aren't always an indication of high pressures, I would still give that some consideration, thus reviewing your powder charge and seating depths just to eliminate some variables.

 

[ThumperACC]

Hi gamestalker,

No signs of high pressure (no flattened primers [not even those not perforated], no bright rings just above the casehead, avg velocity is in line with published numbers). I'd not heard of easy chambering of the fired case being a sign of high pressure so I've not checked that.

My OAL 2.215 is right at the published number and my rounds vary by +/- 0.002". I've always known that seating deeper increased the pressure but had no idea how much. Thanks for the numbers above, it's always good to know things like that. My powder charge is above the midpoint in the published range but not max.

Thanks again for all the info and the thoughtful response,
ThumperACC

 

[243winxb]

CCI400 Small Rifle primers have thin cups like rem 6 1/2. Change primers to mag. or Military Primers #41. Note that Remington states that the 6 1/2 primer is not to be used in the 223/5.56. The firing pin nose will be damaged with a lot of pierced primers. Make sure the primers are being fully seated and that the dillon seating plug is not deforming the primers with a burr on the plug.

[/URL][/IMG] Click for larger pic.

 

[amlevin]

For this, among other reasons, I have started using the Wolf/Tula .223 primers. Thicker cup and less chance of a slam-fire while not as expensive as the CCI-41's.

 

[rcmodel]

5. Weak firing pin spring.

AR-15's don't have firing pin springs.

When it's all said & done, check the firing pin tip under magnification for erosion on the tip.

If your primers have been leaking very long?
The firing pin will show some erosion and you need to replace it.

A rough eroded tip will cause perforated primers, and the problem will feed on itself and get worse, no matter what kind of primers you use.

rc

 

[bigedp51]

Quote:
5. Weak firing pin spring.

rcmodel
AR-15's don't have firing pin springs.

Your correct BUT a weak firing pin hit can still cause this problem.
Sorry I do not own a AR-15 at present because I dislike firearms that throw my brass away.

 

[gamestalker]

I had a very small chip in one of my FP's and it was punching primers. Replaced the FP and no more punched primers.

 

[Waywatcher]

CCI400 Small Rifle primers have thin cups like rem 6 1/2. Change primers to mag. or Military Primers #41. Note that Remington states that the 6 1/2 primer is not to be used in the 223/5.56. The firing pin nose will be damaged with a lot of pierced primers. Make sure the primers are being fully seated and that the dillon seating plug is not deforming the primers with a burr on the plug.

This. I switched to Rem 7 1/2 primers for .223.

I also measure shoulder-bump with an RCBS Precision Mic.

 

[ThumperACC]

Hi RC,

Maybe a total of ~20 rounds with punched primers. I will check my firing pin. I need to get a case gage to confirm that the ~200 rounds I've made with the Dillon are a bit short from case head to shoulder.

I've never seen this through ~1000 rounds loaded on my single stage setup. I'm guessing my sizing die is screwed down a little too much.

Thanks,
ThumperACC

 

[ThumperACC]

Big Ed,

Can you elaborate on this?

"Your correct BUT a weak firing pin hit can still cause this problem. "

I don't think I understand why a weak firing pin hit can cause a perforation.

Thanks,
ThumperACC

 

[bigedp51]

ThumperACC

Think of a innie and outie belly button.

On the hard strike and head gap clearance the firing pin acts like a cookie cutter and punches the primer dent "into" the primer.

On the weak hit and if the firing pin moves to the rear the primer dent is pushed "out" of the primer by chamber pressure.

All of this is controlled by firing pin protrusion length, head space, head gap clearance and chamber pressure. Its all up to which way the primer dent moves after it is hit.

In a nut shell this is why military primers are crimped or staked, it keeps the primer from moving in a military chamber with lots of head space once the firing pin hits the primer.

Note: On a tightly head space rifles the chances of this happening are greatly diminished. "BUT" if the shoulder of the case is pushed back too far during resizing you will have the same problem as a long head spaced rifle. Hence the terms pierced and blown primers or the direction the donut hole moves. (innie or outie)

 

[ThumperACC]

Thanks Ed, that makes sense.

ThumperACC

 

[243winxb]

Pierced or Blanked Primers.

1. Check the firing pin, it should have no gas cutting or deformities. 2. Firing pin protrusion should be checked. Internet search shows .055" to be about right for an AR15. Check with a gun smith as each firearm might be different. 3.The firing pin must stay in contact with the primer on firing. A weak hammer spring on an AR or a weak firing pin spring like on a Rem 700 bolt action will let the firing pin rebound on primer piercing when the hot gas pushes the pin backwards. 4.If the hole the pin sits in is to large in diameter, the primer flowes back into this hole till the center of the primer separates and fall into the action or travels into the firing pin area. Bushing the firing pin hole will fix this. Or you may want to try a magnum primer with a thicker cup.

[/URL][/IMG] Click for larger photo.

 

[W.E.G.]

I had a huge problem with this in my AR15 back in the 90's.
Burned up several firing pins and bolt-faces before I got smart.

Non-magnum small rifle primers are too thin for anything but mild .223 loads.

Switched to MAGNUM primers, and problem solved.

The chronograph showed the velocity of the load to be unchanged when we switched to magnum primers.