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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.

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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.

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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.

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Originally Posted by websterparish47
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.

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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.


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



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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.


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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.


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Originally Posted by FC363

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.


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

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Originally Posted by Swifty52
I would go with some CCI 41's. That's what they are for IMO. But mag primers wouldn't be a stretch either.


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


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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.

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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.


You didn't use logic or reason to get into this opinion, I cannot use logic or reason to get you out of it.

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

Chrono would be good.


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Quote
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,


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.



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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.



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Originally Posted by JackAZ
Originally Posted by FC363

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.


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


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.


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Originally Posted by colodog
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.



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.

[Linked Image]

...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


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Originally Posted by steve4102
Originally Posted by colodog
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.



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.

[Linked Image]

...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.


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Originally Posted by denton
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.


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.

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Originally Posted by JackAZ
Originally Posted by websterparish47
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.


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

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