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

Looking for some insight here…I recently purchased a CZ 527 youth carbine chambered in 223. One of the selling points for me was CZ’s literature in which they repeatedly make the claim that this rifle is designed to handle ammunition loaded to 5.56 pressures. This was important to me because this will be a youth deer rifle that I plan to load with Barnes 62gr TTSX, and that extra 150fps from the 5.56 should get us the expansion we need on that bullet out to 300 yards. I’m in Arizona, so that extra 50 yards can make all the difference on a long desert shot.

Looking at the published 5.56 data for this bullet with TAC, it appears that Barnes and Western Powders are not in agreement. The Barnes data has a max charge of 27 gr, and the powder manufacturer lists max at 26.7. I decided to use the more conservative data from Western Powders as my benchmark.

I loaded up a few rounds using a powder charge one grain below the lowest published maximum using CCI 400 primers and once fired Lake City brass. The first two shots had cratered primers and the third shot pierced the primer. I stopped right away. What was strange to me was that none of the primers flattened very much. All of the pressure sign was in the pin strike. I figured this was my fault for not starting with the min load and working up, and decided to reduce the charge even more at my next trip to the range.

The next time out I loaded several rounds 1/3 of the way between min and max. I didn’t get any pierced primers, but all four primers had cratering, they were still not what I would call flat. My buddy has the exact same rifle, and when we tried them in his, the primers looked exactly the same, so I’m not inclined to believe that it is a firing pin issue.

So now I’m starting to think that CZ must just be full of it by saying that the rifle is designed to handle 5.56 pressures, but just to make sure we retrieved 10 rounds of factory M855 from my buddy’s stash. They worked flawlessly. No pressure signs. Pin strike looks perfect. Primer appears as one would expect.
The M855 should have been higher pressure than the handloads, so I don’t know what to think.

My guess is it’s either:

1) Something about how I prepared the LC brass is causing a primer seating issue. I used the reamer on the RCBS casemate.

2) Perhaps the CCI 400 does not handle 5.56 pressures very well? The M855 had a mil-spec primer on it, so could that be the difference? Should I try the load with CCI 41 primers?

3) Maybe TAC is just a whole lot hotter than the data would suggest? I’m also shooting them on days over 100 degrees, but the M855 was fired on the hottest day of them all.

I’d welcome any thoughts.

I should add that when I load 55gr FMJBTs at standard 223 pressures using the same brass prep technique and using the same primers, I do not see any cratering whatsoever.

I had one of those for a short while. Found it would throw 62gr factory ammo through the target sideways at 25 yards.

CZ hedges a bit saying the rifle will handle 5.56 PRESSURE while not saying it will handle 5.56 ammo.

WAG, the primers are a little thin. Seems all the manufacturers have had that problem lately.

A few years ago they started putting 1:9 barrels on the 527. One reason I am hoping it's the primer and not anything else is that the groups I got with the 62 gr TTSX loaded for 5.56 were amazing.

Are you sure your brass is not too long?
If it's OK, you may want to start your work up over with mag primers. They should handle the pressure better as IIRC the cups are thicker.

I would go with some CCI 41's. That's what they are for IMO. But mag primers wouldn't be a stretch either.

My advice is to find out if the problem is pressure, or primers. The way to do that is take your decapping rod out of your die, and see if you can push the primer out by using the palm of your hand. If you can push the primer out, the pocket has swelled. If you have to use the press to get it out, then see if you can seat the primer with your finger. What you are looking for is an expanded pocket that means the pressure is too high. If the pockets are still tight, then get some CCI41's, or some Remington 7 1/2's.

I have the same rifle. Never pierced a primer with it, but have opened a few primer pockets along the way testing different powders and bullets.

In an AR-15, with a floating firing pin, what you describe is normal when using CCI400 primers, even at 223 pressures.

As you creep up in pressure, the first thing that happens is that the primer strike dimple starts to turn inside out, returning almost to its initial position. Then, the dimple turns inside-out, producing a nipple on the primer. Just a little more, and the nipple fractures around its base, freeing a small piece of primer to fall into your action.

If this is your problem, then a switch to CCI450 or other thick cup primers will cure it.

Have you attempted to load to 5.56 pressures with your rifle?

Swifty, I think 41's are magnum primers, at least CCI says to use magnum primer data.

41s are magnum equivalent. Their cups are thick to prevent slam fires (and maybe add a little bit of drop-safeness) in ARs, which have floating firing pins. I'd expect they are loaded in any factory Federal 5.56 ammo.

Do some googling on primers. There are places where you can find all the cup thicknesses, etc. for the various brands and specs.

Or just back down to starting loads and work up again with 41s or 7 1/2s.

1:9 should work well with 62 TTSX.

Jack,

I wish you had shot those over a chronograph so we could have an idea how hot your load is in YOUR rifle.

I use the full range of CCI primers at max 5.56 pressures in a variety of rifles and have never experiences and issue that was not user induced.

Generally when you load to excess pressures, CCI primers will not puncture. The point of failure will be primer exiting the primer pocket. With Winchester or Federal primers, I've found they puncture before the exit the primer pocket.

Just reduce your load and work up again... Not difficult. Data is a guide.

Chrono would be good.

Well, the rifle didn't fail and it didn't come apart in your hands, so I would say that your CZ rifle does indeed handle the higher 5.56 pressures.

How far off the lands are you with this Barnes bullet?

What velocity are you getting with these 62gr Barnes loads?

The Ramshot 5.56 data was most likely tested in a 5.56 chamber. The 5.56 has a longer throat than most 223 chambers. Using 5.56 pressure loads in a short throated 223 chamber can cause an increase in pressure.

Another vote for, Use a Chronograph!

Look at it this way, the book says they reached max pressure with ABCD load, producing XXXX speed, in their rifle.
If you're not using the same primer and brass as the load manual it's not really the same load.
If you can't measure velocity, all we, or you can do is guesstimate.
Barnes bullets recommends their bullets be seated +-.050" off the lands for a running start, something to check.

Military brass is usually heavier and won't hold as much powder as commercial brass so dropping one grain may not be enough, I don't know!
You'd need a Chronograph to compare a single load between military and commercial brass. (I'll be checking 30-06 myself)

Lastly, your buddy's M855 ammo wasn't shooting monometal bullets which are usually longer than lead/steel core but you can't compare velocity anyway without a Chronograph.

If you are piercing primers in a load that shoots 5.56 ammo with no problems, then you are either over pressure, or your primers are the wrong ones.

Although this is true for the 308 and 30-06 Military Brass, it is not true for the 223 vs 5.56 brass.

In fact most military 5.56 brass has More case capacity then civilian 223 brass.

Note in this chart the Military brass had the highest capacity.



...and this from Sierra.

The conventional wisdom to reduce loads with military brass is familiar to most reloaders and is generally good advice. The rationale here is that the military cases tend to be somewhat thicker and heavier than their civilian counterparts, which in turn reduces capacity and raises pressures. This additional pressure normally requires a one or two grain reduction from the loads shown in most manuals or other data developed with commercial cases. While this is most often the situation with both 308 Winchester and 30-06 cases, it is less true with the 223 brass. We have found that military cases often have significantly more capacity than several brands of commercial brass. Again, take the time to do a side-by-side comparison of the cases you are working with and adjust your load as needed. There may be no need for such a reduction with the 223. Know your components and keep them segregated accordingly.

http://www.exteriorballistics.com/reloadbasics/gasgunreload.cfm

I've checked the H20 capacity of Remington brass, and also got the same 30.4 gr listed above.

I believe that pressures can cause cratering even with an AR, I was testing some loads the other day and when I went home I checked the cases and noticed that all of the primers had slight cratering and most had case head swipe, backed off three tenths of a grain and shot them, cratering and case head swipe disappeared. I was using Cci 400 primers, it is possible that with another primer things might be different but with both cratering and CHE evidence would point to slightly excessive pressures. If you send me a PM I can give you more details regarding the load.

I think shooting 5.56 rounds in a 223 chamber is a bad idea.

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.

The copper crusher system was designed to give results in PSI, and at lower pressures, it does pretty well. When piezo measurement gear became available, it was found that at higher pressures the copper crusher system seriously underestimated PSI. Still, back in the day, copper crusher numbers were commonly reported in PSI. P O Ackley's book is full of "PSI" numbers that were produced on a copper crusher system. If you see an old standard or number, it's hard to tell whether it's from the old system or the new one, since both are reported in the same units.

The military did not use the SAAMI copper crusher system. They had their own way of doing it. Military copper crusher numbers are not the same as CUP.

Exercising a bit of Google-fu: SAAMI puts the piezo transducer in the middle of the cartridge and rests the piston on the cartridge case. CIP in Europe drills a hole in the cartridge case so that the piston is in contact with the gas, with no brass in the path. NATO EPVAT puts the transducer at the mouth of the cartridge. The US military used the SCATP method, which is similar to SAAMI.

So, there you have four different piezo methods, and at least two different copper crusher methods. Small wonder it's confusing.

Now, is the 223 loaded to the same pressure as 5.56? I have believed that they are not. However, in light of today's exercise, and the fact that brass in the pressure path reduces readings by about 5-7000 PSI, I suspect that Ramshot's 5.56 loads might be in error. It seems possible that they have used the CIP number and the SAAMI test procedure.

So the definitive answer will probably come from someone chronographing American Eagle 223 ammunition vs. American Eagle 5.56 ammunition. They are both made at Lake City, and if anyone understands military vs. SAAMI tests, it would be them.

The military did use the copper crusher system of taking chamber pressure. If you look at military SCATP standards it simply states that SAAMI standards will be used for taking chamber pressure readings.

And as I stated earlier I have the milspec requirements for commercial contract ammunition made for the military. And the requirement lists 52,000 cup or 55,000 psi for 5.56 ammunition.

The only difference between the .223 and 5.56 are the throats. Now look at the first information at the link below for my Savage .223 throat that is longer than the throats in my AR15 rifles.

HOLLIGER ON .223/5.56 CHAMBERS (Savage .0566 and AR15 .0500 throat length)
http://www.radomski.us/njhp/cart_tech.htm





The throat in my Savage is big enough for the M855 cartridge with room left over for the Savage company lawyer. Meaning its the shorter throats that will cause the pressure spike when firing 5.56 ammunition.

And you do not need to test any ammunition yourself, it has already been done, and all you need to do is read.

5.56 vs .223 – What You Know May Be Wrong
http://www.luckygunner.com/labs/5-56-vs-223/

That Lucky Gunner article is very helpful. Thanks for posting.

The author makes the point that he used two different 5.56 chambers during testing, and his first pressure graph does not stipulate that he used the same FN chamber for comparisons of 223 and 5.56 pressures. But from the context, it appears that he probably did.

If so, 5.56 is loaded to higher pressures than 223. That is what I had believed, but started to question in light of my recent suspicion that the Ramshot used CIP/NATO spec numbers and SAAMI test methods, which is a no-no.

The one big error I see in the Lucky Gunner article is that he did not appear to control barrel and ammo temperature. When I do strain gauge measurements, I stick a thermocouple to the barrel just ahead of the receiver. That gets rid of a substantial amount of measurement system error.

I have a note in to Ramshot. Maybe we can get some clarification from them on how they did their data.

Back in '02, when I did my article about converting CUP and PSI, the 223 Rem 55,000 PSI:52,000 CUP data pair was an outlier that did not conform with the rest of the data. Since it was the oddball of the data set, I took it out. In general, 55,000 PSI is equivalent to 48,300 CUP. I have no idea what kind of jiggery pokery produced the 52,000 number.

Anyway, although we're having great fun, we've drifted far from the original question.

OK, one last bit of info... then I gotta go earn a living.

Ramshot wrote back:



So they are not mixing CIP/NATO numbers with SAAMI test procedures.

5.56 is loaded hotter than 223, and it's OK. The snail is on his thorn, God is in His heaven, and all is right with the world. Well, except for our politics....

When you fire a 5.56 M855 cartridge in a military chamber with its longer throat the chamber pressure is 55,000 psi.

When you fire a civilian .223 cartridge in a civilian chamber with a short throat the pressure is still 55,000 psi.

Meaning military 5.56 ammunition is not loaded to higher chamber pressures. "BUT" if military ammunition is fired in a civilian short throated .223 the chamber pressures will be higher. And the throats are what cause this change in pressure readings. And the European CIP considers the .223 and 5.56 cartridge to be one in the same.

The SAAMI interchangeability warning between the .223 and the 5.56 did not come out until 1979. And it was at this time the military introduced the M855 cartridge and M16 rifles with a longer throat.

The SAAMI sets guidelines for chamber dimensions and the gun manufactures are free to change chamber and throat dimensions as they see fit.

I can load my Savage .223 hotter than listed loads in reloading manuals because it has a longer throat than either of my AR15 rifles.

And the max load for the .223 with 55 grain bullets in the Hornady manual is 23.2 grains of H335. And the max load for 55 grain bullets and H335 in the Sierra manual is 27.5 grains.

I will take a wild ass guess and say the difference in these two .223 rifles is throat length. And a good reason why they say to start low and workup when reloading.

Now look below at all the different throat lengths and diameters. My off the shelf factory Savage .223 has a .0566 length throat the same length as the PTG and JGS NATO chambers. And its the .0250 length throats that will cause the higher pressures and possible problems. And not by people guessing about how the pressure is measured in what type chamber.

That sounds reasonable, within the limits of measurement precision.

But you are confounding two variables, throat length and cartridge load. That needlessly confuses the issue.

A simpler way of stating it is, for any given chamber, 5.56 loads will produce higher pressure and velocity than 223 loads.

Throat length is a separate variable. Shorter throats produce more pressure and longer ones produce less, all other factors equal.

If the Lucky Gunner author had been just a trifle more clever he could have done a balanced experimental design and cleanly separated those two variables.

And I do think the issue is a bit overblown. When I was working on an M855 problem at Lake City, we ran thousands of rounds heated to 150-160F, with the rifles at the same temperature. We weren't testing MV or pressure, but those temperatures had to be producing some serious out of limit conditions. We had no problems. I suspect that the SAAMI spec may be pretty conservative compared with other cartridges.

I suspect you are right.

55k PSI is pretty anemic in a modern rifle.

Good discussion. Interesting points have been brought up that beg for definitive answers. I want to be right, but I'm not so sure I'm really that close. I'd like to see all these disparities resolved, but simply in the interest of truly knowing, which isn't the same thing as believing. You guys have a great evening.

Let me piggyback on what has been an interesting thread here if I may. Ramshot moved the target on me. I have an older Ramshot loading pamphlet. It lists a max load of TAC in 223 (not 5.56) pushing a 60 grain bullet at 26.7 grains and a starting load at 25.4. I split the difference and built some loads with 26 grains using Remington 7 1/2 primers. I haven't fired any yet. Today I was skimming TAC loads on the Ramshot download and it lists a max charge of TAC pushing a 60 grain bullet at 24.8. Similarly I built some loads using 50 grain bullets and those loads too are beyond current Ramshot max loads. My launch platform is a Remington SPS.

I spent a while looking at TAC loads on various forums and have found some that show my loads as OK and have found some that show my loads as over max. Any thoughts?

Nosler also lists 24.8 grs TAC with 60 grain bullet rem 7 1/2 primer. So its your call. personally I would load up some lighter charges and work up and see what happens. Again its your call.

Paul, I'd start with the latest Ramshot online loading manual. They provide data for both .223 and 5.56 loads. Keep in mind, bullet selection matters. As an example Hornady Vmax typically have a greater bearing surface then a Nosler Ballistic tip of the same weight. Consequently, if I work up a load with NBT's, I'll back off a grain if I switch to the VMAX.

My apologies, I stepped away from this project for a while and neglected to see that there was still ongoing discussion here.

I searched around a bit and came to the same conclusion that I should try a different cup thickness. One of the sources was the James Calhoon article that I believe is also the source of one of the charts you posted. http://www.jamescalhoon.com/primers_and_pressure.php

This past week I had a chance to make some new loads and to swipe by buddy's new magnetospeed chronograph. I used the same mid-range 556 load (according to Ramshot data) that was causing cratering, but I loaded them with CCI 41 primers. With the thicker cup I got zero cratering, primers that still had a radius on the edges, and groups under 3/4" at 100 yards. When I put the magnetospeed on the barrel I got readings of 3090, 3097, and 3095...which is exactly what I had expected (and hoped for) based on the pressure that should be there.

Thanks again for the advice. These loads will only be used for hunting. I wanted the extra velocity of 556 pressure to make sure that the Barnes TTSX opens up out to 300 yards. All of the plinking and practice will be done with my usual 223 reloads...which are mild and do just fine with CCI400s.