Home Forums Reloading Big Game Rifles Cratered and Pierced Primers - Advice Needed

Agreed, but if you read the OP you'll see that the manufacturer insists (in several published places) that the chamber is actually cut to accept 5.56.

The chamber pressure of the .223 and the 5.56 are both 52,000 cup or 55,000 psi. The actual difference between the two is the throat and the shorter .223 throat will cause a pressure increase with military 5.56 ammunition.



The CCI 400 primers you are using have a cup thickness of .020. Just switch to a primer with a cup thickness of .025 and your primer problem will go away.



I would also advise using workup loads starting at the suggested start load and work up. This will teach you how to read your primers as the load increases.

Also your pierced primers are a sign you are bumping or pushing the shoulder back too far when sizing.

The primer after being hit by the firing pin will be pushed out of the primer pocket until it contacts the bolt face. This causes the primer to flow back over the firing pin and it can punch the center out of the primer.

Headspace is often over looked..

This is one of the subjects I have spent an inordinate amount of time researching. If you dig and dig and dig some more, you'll find electronic copies of military specifications and standards.

Based on what I've been able to find so far, NATO uses pressure measurement techniques specified in the EPVAT standards and the method is very similar to the CIP methods. These numbers tend to run around 62000 psi.

The US Military uses the SCATP standard. The pressure measurement technique specified therein is very similar to the SAAMI pressure standard. Up until fairly recently these numbers remained around 55000 psi. I say "until fairly recently" because I have found that the US military has upped the pressure limits somewhat. An example would be the M855A1 round, and I think they've allowed pressures of over 58000 psi as measured using SCATP methods.

Then again, when you get to looking at all these different documents there are ranges of allowable pressure variance, and it gets a bit complicated for a non-statistician such as myself.

Here is a list of the document titles I have found so far (google may be your friend), if anyone's interested:

MIL-C-9963F
MIL-C-9963F_AMENDMENT-1
MIL-C-9963F_AMENDMENT-2
MIL-C-9963F_AMENDMENT-3
MIL-C-9963F_AMENDMENT-4
MIL-C-9963F_AMENDMENT-5
MIL-C-9963F_NOTICE-1

MIL-C-63989A
MIL-C-63989A_AMENDMENT-1
MIL-C-63989A_NOTICE-1
MIL-C-63989B_AMENDMENT-1
MIL-C-63989C
MIL-C-63989C_AMENDMENT-4-1
MIL-C-63989C_NOTICE-1

MIL-C-70460A(AR)5Oct1984
MIL-C-70460A(AR)15Oct1999

I think these all relate to the subject of 5.56 ammo, but I did not open them all to verify. Not on this junky old computer! If some of the docs are not relevant to the subject, hopefully you'll find them to be interesting anyway.

If someone uncovers more such stuff of an authoritative nature, I'd be most interested in taking a look at it myself.

RiverRider

The secret to understanding .223/5.56 chamber pressures is to remember your an American and our speed limit signs are in MPH and not KPH. Meaning it doesn't matter how Europe measures chamber pressure we Americans use two methods. The copper crusher method (CUP) or copper units pressure or the transducer method that measures pressure in PSI or pounds per square inch.

Below is the milspec standard for commercial ammunition made for the military. At 3.7 the chamber pressure is listed as 55,000 psi SAAMI transducer method.



Now look below at the .223 with the SAAMI and CIP standards.

Cartridge Pressure Standards
http://kwk.us/pressures.html

Bottom line American 52,000 cup, 55,000 psi and European 62,000 psi are all three the same pressure measured three diffrent ways. Or back to the speed limit signs 60 mph = 100 kph are both the same speed.

And below from the Army TM 43-0001-27

Yes, that's the meaning of what I said. I may not have been very clear, though.

JackAZ

You are using CCI 400 primers with a cup thickness of .020 and would be much better off using primer cups of .025 thickness.

Question, how are you sizing your cases, meaning minimum shoulder bump of .001 to .002 or sizing the case with the press reaching cam over and maximum shoulder setback.

Over resizing your cases creating excessive head clearance and thin primer cups could be causing your pierced primers.

When you push the case shoulder back too far your create excess head clearance at the rear of the case. This allows the firing pin to act like a cookie cutter and punch the center out of the primer as the primer moves to the rear and contact the bolt face.



Below a case fired in a AR15 rifle, the primer cup was too thin and the case shoulder was pushed back too far. The AR15 rifle is over gassed and the bolt can move to the rear while there is still pressure in the barrel. And this allowed the primers anvil to poke through the hole in the primer.



I would advise getting the Hornady Cartridge Case Headspace Gauge to control shoulder bump.

Below a fired case from my AR15 carbine.



And the same case after sizing and .003 shoulder bump.



NOTE: I have a Lee full length .223 die if set up as per the instructions and reaching press cam over will push the shoulder back .011 shorter than its fired length. So watch your shoulder bump.

I wouldn't load without it.

If memory serves correctly, CIP in Europe does their piezo pressure test with cartridges that have a hole in the case that aligns with the hole in the chamber. So if I'm not confused, their pressure transmission rod is exposed to the gas without cartridge brass in the way.

Cartridge brass reduces the measured pressure by about 5-7000 PSI.

Thank you for stimulating my gray matter again, too much of what I absorb leaks out of my ears over time.

CUP vs. PSI — What’s The Difference in Pressure Measurements
by Philip Mahin, Sierra Bullets Ballistic Technician

http://bulletin.accurateshooter.com...the-difference-in-pressure-measurements/

Note to all, Accurate Shooter is a great place for reloading info. Just remember to wear ear plugs and not loose it all.

I believe the location on the chamber differs also between CIP and SAAMI methods.

Correct and not only are the points on the case where the pressure is taken in diffrent locations the pressure traducers are themselves designed differently.

So again forget NATO pressure standards, we are Americans, our speed limit signs are in mph and not kph and the American SAAMI decides the standards of testing here.

And our Army doesn't separate "HOW" the chamber pressure are taken. Meaning in the manual below the copper crusher method and transducer method are just listed as PSI. I have an older milspec document like I posted before that lists both methods and the pressures of 52,000 cup or 55,000 psi.

Below chamber pressure taken with newer transducer method.



And chamber pressure taken with the older copper crusher method.

How do you like that.

MIl-spec is 28.5gr of WC844 (H335), with a 55gr bullet.

Military lots if WC844 can vary in burn rate, meaning it can be slower or faster burning than H335. While civilian H335 will remain more constant in burning rate.

And as one person said in another forum he would rather make one workup load for H335 than work up loads for every jug of WC844 he buys. Meaning the military adjusts its loads for each lot of WC844 and the charge weight of 28.5 varies.

What??

I'd beg to differ with you. SCATP specifies very exactly how chamber pressures are measured, among other things.

It sounds as though you do not understand "standards" at all. A standard specifies exactly how something is to be done and exactly what equipment is to be used. Standards may change over the years and specify different equipment and numerical values (such as pressure, for one), but that's why they put dates on them.

The ANSI/SAAMI piezo standard is to measure pressure with the wall of the case in the pressure path.

There are at least two other piezo standards. One measures pressure with the rod through the case, directly in contact with the powder gas. Another measures pressure at the mouth of the case, presumably without brass in the path. Tonight, I'm not quite ready go detangle which standard is which.

5.56x45 ammunition produces higher muzzle velocity than 223 with the same type of powder and the same bullet, so the actual pressure produced by 5.56 has to be greater than that produced by 223.

Lake City 5.56 brass has more case capacity than any other type I have tested, except Federal. I don't think the small difference in capacity is enough to account for the difference in MV.

CUP and PSI are correlated. Both systems show monotonically increasing values with increasing powder, i.e. you add more powder and both CUP and PSI go up. They must therefore be correlated. It gets confusing because both systems have considerable random noise, resulting in some values that seem out of line. But if you graph CUP vs PSI over a broad range, the correlation is obvious. If you estimate PSI from CUP, you'll get an estimate that is almost as good as estimating the PSI reading you'll get from the previous sample of PSI. I did an article on that a few years ago, and took a fair amount of flack. Later on I discovered that Dr. Brownell estimated the relationship at least a few decades earlier.

The OP's piercing/cratering problem might also relate to shoulders being bumped back too far, but the standard for M16 ammunition is thicker primers. Use regular primers, and you'll very often see exactly this problem. #41 primers are standard for the round. Regular small rifle primers are not. Switch to #41 primers, or to CCI 450s, and chances are the problem will vanish.

The M16 has a floating firing pin. It is not unusual at all to find a tiny dimple from the firing pin on the primer of a round that was chambered and then ejected without firing. To prevent accidental discharge when the bolt is released, the system is designed to use thicker primers.

Okay, maybe we're getting somewhere here. Agree with you on the velocity/pressure thing. What specific 5.56 ammo are you referring to, and can you link to an actual document? And how do you say "5.56x45 ammunition produces higher muzzle velocity than 223 with the same type of powder and the same bullet" unless you know what powder is used in both types of ammo? Who produces SAAMI spec .223 Remington using WC844, WC 846, or whatever, and what factory producing .223 Remington tells you what powder they are using?

Excellent question.

Just check the Ramshot loading data for 223 vs. 5.56.

Ramshot TAC, Hdy BT-FMJ 55 grain bullet, max load is 25.8 grains for 3293 FPS in the 223. In the 5.56 it is 27.3 grains for 3450.

As an alternative, you could chronograph American Eagle 223 ammo vs. American Eagle 5.56 ammo. They are both made at Lake City, on the same equipment, and they do mark the boxes differently. I haven't performed that test, but it would be interesting to know

The military specifies that when testing the ammo the copper crusher or transducer method may be used. As you can see from the sheets above one is listed as 52,000 psi and the other is 55,000 psi. Meaning the 52,000 psi reading was tested using the copper crusher method and the 55,000 a transducer was used. And the Army uses psi in both pages.

So I do understand the standards, BUT the Army doesn't write cup after the pressure figures if the copper crusher is used.

Therefore I understand 52,000 cup is the same pressure as 55,000 psi and the Army does not separate which method was used.

All SCATP states about chamber pressures are that SAAMI guidelines will be followed by the military.

Meaning the .223 and 5.56 are both loaded to the same chamber pressures. The only differences being the throat of the two chambers.