I have been reloading for a while and have not really pushed load limits.  However I am starting to reload 300BLK.  Some of the data I am seeing is above MAX recommended loads from the manufacturers of components.

I noticed on all .223 I shoot (factory or mine) do have some flattening of primers-especially NATO stuff.  I can still see a little space between the primer and case but not a lot.  I am not talking primer flow but how much is OK?

Reading primers isn't an exact science. That being said it's hard to even make a guess without knowing what primers you're using

There is not a good answer to your question. One reason is primers are too different from one brand / type to another. Plus there are several other factors that can make a primer flatten.

Bottom line is, reading primers alone is not a very good way to judge your loads.

Data research from as many sources as possible and a chronograph is the best way to monitor your loads.

I won't shoot any load that flattens primers. There is no reason to. I normally use Remington 7.5 primers and they are as tough as any on the market when it comes to maintaining their integrity under a decent load of powder. Russian 556 and magnum small rifle primers are good, so are CCI-BR4's, 450 and #41 military primers. If I'm getting flattened primers with any of these I need to back off my powder charge.

Some rifles simply will not handle certain powder/primer/bullet combinations without showing pressure signs. Trying another powder sometimes clears things up. 300 whisper/aac/blackout all use pistol powders which are much faster burning than standard rifle powders and will spike pressures accordingly. Drop your powder charge at least .5 grain and the flattened primers should clear up.

As stated above it is tough to say when they are too flattened. Here is what I do with every gun I load for.

I shoot a selection of factory ammo and measure case expansion at the web. I also make a mental note of the primer condition.

Primers that are flattened don't really worry me. Most primers will flatten to some extent. When the start to flow to fill out the primer pocket I know I have gone too far. I use that, case head expansion, velocity and accuracy to keep things safe.

FWIW, I have only found a couple bullets that did well at max. In my experience most like to be somewhere below max for best accuracy.

That's what I mean. All cases I shoot flatten primers to some degree. Factory or reloads. Factory, etc. Just don't know what is too much I guess.

Thanks for all the replies.

I just posted this in the blackout thread wondering if they are too flat ?

Wag? Primer 2, 3, 7(?) & 9 would make my list.

Some of mine look like those but not the flattest ones.

Are all I those the same loads?

Looking at the primers above, if they were all from the same load, I'd back the load down, and select a more consistent powder for the load as well.  

Of the cases pictured above, I'd be ok with 1, 4, 5 and 8, the rest are way too flat to even think about kidding your self about safe pressures.  By the time you see any signs of excess pressure in a .23, you're already well over SAAMI's pressure specification.  

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There is variation in the pressure from shot to shot with most loads, but you still want to keep the maximum load on the safe end of things.

For example, the specifications form M193 call for:

1. an average velocity of 3165 fps (20" barrel measured at 78 ft from the muzzle), plus or minus 40 fps, with a standard deviation of no more than 40 fps.      

2. a maximum average chamber pressure (piezo electric measurement) of 55,000 psi with maximum average pressure plus 3 standard deviations of 61,000 psi (the specification is designed to control both the average pressure of the load, but also to keep the range of pressures acceptably narrow with a standard deviation of 2,000 psi, which essentially means that 67% of the rounds fired can be expected to have a pressure between 53,000 psi and 57,000 psi, but about 2 percent of them will have pressures as high as 61,000 psi); and

3. an average port pressure (20" barrel, via piezo electric measurement) is 14,000 psi +/- 2,000 psi

The M855 specs are slightly different with:

1. an average velocity of 3000 fps (20" barrel measured at 78 ft from the muzzle), plus or minus 40 fps, with a standard deviation of no more than 40 fps;

2. a maximum average chamber pressure (piezo electric measurement) of 55,000 psi with maximum average pressure plus 3 standard deviations of 61,000 psi; and

3. an average port pressure minus 3 standard deviations of not less than 12,700 psi.

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The major issue I have with many reloaders who want to push their .223/5.56mm NATO loads is that almost none of them have any way of measuring pressure at any point along the chamber, barrel or gas port,  and the majority of them don't even own a chronograph and/or don't know how to use it and properly interpret the results.

The end result is threads like this with pictures like the one above that suggest a too hot load that also has an unacceptably large variation in pressure.  IMHO it's a really shitty load that I would not even consider feeding to any of my AR-15 based weapons.

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Personally, I see absolutely no reason to "push" a .223 or 5.56mm NATO load hard enough to flatten or crater a primer.  If you really need improved down range performance or flatter trajectory over a longer distance in an AR-15, use a more efficient bullet and cut back on the velocity a bit to eliminate any signs of excessive pressure.

Many AR-15 shooters, particularly the retro crowd are familiar with the velocity problem with the original M16.  The short version is that the original 55 grain .223 round loaded to the original maximum pressure standard would not pass 300m penetration requirement.  The result was a waiver allowing another 1000 psi of pressure.   However, the cause of all this was not the powder or case, but rather the design of the 55 gr projectile Remington chose for production.  It was a shorter, blunter projectile with a 5 caliber ogive, and was not as aerodynamic as the slightly longer 7 caliber ogive projectile stoner used when the cartridge was designed to meet the specifications.   The result was the less efficient bullet needed more velocity to meet the 300m penetration requirement.  A far more elegant solution for Remington and the US Army would have been to select and specify a 55 gr projectile with a higher BC.  

That's the same elegant solution that works for a hand loader as well if they really have to have maximum down range performance from a .223 - use the slickest bullet available in what ever weight range you require and focus on optimum accuracy within 100 fps or so of maximum with no pressure signs, rather than trying for maximum velocity.

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If you are going to seek the limits of any cartridge you also need to buy and learn to use a chronograph.  Among other things it will give you some pretty reliable indicators of whether your load is performing as expected in terms of velocity, and it will tell you how consistently the load is performing.  It's not exact, but generally speaking a load with a low standard deviation in velocity will also have commensurately low standard deviation in pressure.  In terms of standard deviation, less is more and I like to see my .223/5.56mm AR-15 standard deviations down around 25-30 fps and I shoot for about 15 for in target and match loads in a 20" barrel. (In general, a longer barrel will result in a lower SD, all other things being equal).

I also shoot for minimum group size when developing a load and on each rung of the ladder, I'll shoot three 5 shot groups, all over the chronograph to get a total of 3 group measurements and a 15 shot velocity sample to compare with other powder charges on the ladder.  I STOP TESTING as soon as I discover any round with signs of excess pressure (primer flattening, primer cratering or head expansion) OR if I detect any indications of a rapidly increasing variation in velocity.

After I select a couple of the best performing finalists from the ladder, I'll repeat the three 5 shot routine, giving me a total of 6 groups and 30 shots for SD measurement as a minimum before I start any kind of large production of the load.  If I plan on making a lot of rounds, I'll do another test with 30 production rounds, again recording groups size and velocity.

And that there is great info.  Thanks for your thoughts.

+1 on loading for accuracy

and

+1 on there being a number of factors that can lead to primer distortions.    Oversizing brass and/or factory ammo in some cases .... IE. shortening headspace measurements down to minimums to better insure function in a multitude of rifles and/or reducing liability for a die maker  .... can also contribute to primer distortions in some cases.    Not saying that is the case in the pictures above though.

Sorry guys I meant to come back and post some info here. The brass above is 300 blackout formed from 223. I just started working on a load with imr4227 and 175 grain SMK's . The starting load was 15.7 and I was getting some signs but the group was ok. I went up to 15.9 and this is what the primers shown. The max load is 16.7 so I was under the max charge ?

Again ... reading primers ain't the best way ... but that said.

Assuming your primer pockets aren't loose, and assuming you aren't oversizing...and more importantly probably, given you were "getting signs" at 15.7 and after going up, got some more signs...assuming everything else was equal ......... then I would say Max in your rifle is lower than max in the rifle tested for the book, and you're too hot.    

Not trying to be a tool, just saying the bread crumbs lead there....but just because that is where the bread crumbs lead, doesn't make it so .... see reading primers ain't the best way.  

The poster above's discussion about other less subjective data points like velocity is good stuff.

Also reiterating that there are too many things that can contribute to primer distortions for someone to nail it based on a picture.

the primers in the picture look fine to me, ive had factory ammo that absolutely squishes a primer flat.
look around the edge of the primer and the case, you can still see a gap and the endge of the primer is still round.

when you have a hot load that primer will flatten out so much you wont see a gap between the primer and brass and the edge of the primer between it and the case will not have a rounded edge. it will be flat.

notice how the case on the left has cratering around the firing pin and edges of the primer are flat - hot load
the case on the right still has a nice rounded edge on the primer and no firing pin cratering


The picture above was one I found by googling

Don't expect every load to make it to xx grains per the book. It will happen occasionally but not always. My recent experience loading for my AR10 proves that. My starting load shot great. The next .2 grain step showed 25% of the brass with some primer flattening. Two tenths more and I got 50% flattened. I tested one more step and it was obviously too much. I went back to the starting load and called it good. I didn't run them over the chrony but I am guessing the velocity will be good when I do.

Thanks guys I didn't mean to take over defenderhome's thread hoping that this will answer both our question ?

CCI 400's, rem 6 1\2? I could have missed it, but exactly what primers?

Could be thin cup primers too, showing early pressure signs.

Good discussion so far.  Some of the "flat" ones in your picture look like my precision loads for my .223 bolt gun, and I do push it pretty hard (nearly a full case of varget, with a 69 SMK compressing the load, set off with a BR4 primer).  The gun loves it, and the primers are definitely flat, but aren't starting to crater at all.

One other sign of "pressure" you might look into is an imprint from the ejector pin from your bolt.  This will show up as a small round impression on the case just outside of the primer.  You may also notice a small distortion of the rim where the extractor grips.  It is kind of like the reading primer method though...very dependent on several things, but in general if you are seeing that, you are probably pushing things too far.

Being basically a "old timer" at reloading I get your drift. Reading primers is all we used to have along with the data of course and yes I still do it. If you have a well established base line and good components it can be useful.

The true problem with reading primers is there are just too many things that can give false readings.

False reading can be both ways too not just false flatness. I found this out while working up a load for my 300 RSAUM. My CCI-250s looked just fine but my bolt was a tad tight. The chroney showed 200 f/s OVER MAX velocity. It seems some of the early data was a little hot.

CCI 400's

I have a good chrono and that is why I get confused on the primers.  

All other things within load data limits and I still get some flattening is just what is going to happen.

I see posts with the primers that look like they were shot with super light loads.  I also see most of mine with "some" flattening.  The same flattening occurs when I shoot MilSpec factory loads in several rifles.  These are primers that aren't flowing to the edge of the pocket, I can still see some radius, but not like you can with super light loads.  Some of that is just normal.

OP - Defender

If you are up for it, I'd be curious to know.....

What is the headspace measurement of your specific rifle?

What is the pre fired headspace measurement of the MilSpec factory loads that show some flattening in that rifle?  (They may be all over the place, in which case take ten and note the high and low)

What is the pre fired headspace of your finished reloads that are well below max but still showing some flattening in that rifle?

(Reason for ask ... I believe, rightly or wrongly, that the primer moves before the case stretches when the round is fired.  If there is a, for lack of a better description, a  "big gap" or excessive gap,  those primers will look different then if there is a "little gap".   May or may not be the case here - just curious.  Headspace measurements may not be the best way to quantify the gap either...primers might be seated diff for example)

To Motor1 ... totally agree with you.   I actually don't mind looking at primers and/or discussing what different primer outcomes are caused/or not caused by.  Would rather have people looking at them then not as long as possible conclusions aren't considered holy grail.   But to your point that I agree with, what scares me is when someone is  over max and concludes he is just fine simply because his "primers look good" - false readings....it's a great point to bring up.    Too many times I see people say....go to a stronger primer...when if reality that might just continue to mask that the guy is over already.

Hornady American whitetail are good for flattening the primers and flowing into the firing pin hole on my lr 308.  

Honestly, I don't measure headspace.

I have read up some on it but between functioning well, good accuracy, and no other pressure signs, I just have stayed with being satisfied. When my schedule allows me, I will look more into it.

I do use quality barrels, bcg's, etc. I think I over think what I am seeing in the primers.

Most of my better loads are not pushing max. Actually on the lower side.

Why push that particular envelope?  Hard on the machinery.  Hard on the brass.
Back off just slightly.
IMHO there should be no primer flattening.

Impossible. Unless you are shooting drastically reduced loads. Any normal pressure load will flatten a primer to some degree.

A good typical for design / caliber performance load in a typical bolt action rifle will almost always flatten at least half of the corner radius away.

After looking over all my brass, all have some flattening. I think I am worried over nothing. I think what I am seeing is normal occurrence of the primers.

CCI 400 are thinner cup, and will show "false" pressure (flattening early) signs.

I use Winchester primers